Continuous polymerization apparatus and process for producing polymer composition

ABSTRACT

The present invention provides a novel continuous polymerization apparatus which is able to efficiently produce a polymer composition suitable for obtaining a resin composition with high quality. In a continuous polymerization apparatus, at least, a first reactor of a complete mixing type and a second reactor of a complete mixing type ( 10, 20 ) are used. Each of the reactors ( 10, 20 ) is provided with a supply port ( 11   a   , 21   a ), an effluent port ( 11   b   , 21   b ), and a temperature detecting means (T) for detecting a temperature in the reactor, wherein the supply port ( 11   a ) of the first reactor ( 10 ) is connected to the supply sources ( 1, 3 ) of a raw material monomer and a polymerization initiator, and the effluent port ( 11   b ) of the first reactor is connected through a connection line ( 15 ) provided with a cooling means ( 16 ) to the supply port ( 21   a ) of the second reactor ( 20 ). The cooling means ( 16 ) is controlled to make the temperature in the connection line adjacent to the supply port ( 21   a ) of the second reactor lower than the temperature in the first reactor ( 10 ).

TECHNICAL FIELD

The present invention relates to a continuous polymerization apparatus,i.e. an apparatus for continuously conducting a polymerization.Additionally, the present invention relates to a process for producingpolymer composition which is conducted by using such continuouspolymerization apparatus.

BACKGROUND ART

Resin compositions such as methacrylic ester polymers are produced bycontinuous polymerization in which a raw material monomer, apolymerization initiator and so on are continuously supplied to areactor to be polymerized. As such continuous polymerization processes,there are known a continuous solution polymerization process using asolvent (or a dispersion medium, which also applies hereinafter) toconduct continuous polymerization, and a continuous bulk polymerizationprocess using no solvent to conduct continuous polymerization.

In general, a continuous solution polymerization process is notefficient since use of a solvent causes a low productivity. In contrast,a continuous bulk polymerization process has an advantage of being ableto produce a polymer composition efficiently since the polymerization isconducted without using a solvent. Practically, the continuous bulkpolymerization, however, has various problems compared with thecontinuous solution polymerization, such as that reaction control isdifficult due to high viscosity of a reaction mixture, and when an innersurface of a reactor is cooled to remove heat from a reaction system,this degrades quality of a polymer composition and thus of a resincomposition obtained therefrom. Therefore, a process is proposed whichuses a reactor of a complete mixing type, fully fills the reactor withliquid to exclude a gas phase part therefrom, and conducts continuousbulk polymerization under an adiabatic condition with no heat transferto or from the outside (Patent Literature 1). Further, in order toassure such adiabatic condition, a continuous polymerization apparatusis proposed which controls a supply amount of a raw material monomer anda supply amount of a polymerization initiator so as to make atemperature in the reactor equal to a setting temperature of an outersurface of the reactor (Patent Literature 2).

CITATION LIST Patent Literature

Patent Literature 1: JP 07-126308 A

Patent Literature 2: JP 2006-104282 A

Patent Literature 3: JP 01-172401 A

Patent Literature 4: JP 05-331212 A

Patent Literature 5: JP 2004-211105 A

SUMMARY OF INVENTION

In recent years, applications of resin compositions such as methacrylicester polymers has been expanded furthermore, a demand is increasing formore efficiently producing a polymer composition with high quality (forexample, a polymer composition having superior properties such as heatresistance and thermal stability, and less immixed with impurities).However, it has been proved that the conventional continuouspolymerization apparatus (Patent Literatures 1 and 2) are not alwayssufficient to meet the demand.

The purpose of the present invention is to provide a novel continuouspolymerization apparatus and a process for producing a polymercomposition wherein the process can be conducted by using suchcontinuous polymerization apparatus and more efficiently produce thepolymer composition suitable for producing a resin composition with highquality.

The inventors considered using at least two reactors of a completemixing type in combination to conduct continuous polymerization. As to acontinuous solution polymerization process, apparatuses having twostages of reactors are known, such as that the most part ofpolymerization is conducted in the former reactor and the polymerizationis completed in the latter reactor while removing a polymerizationinitiator and the like therefrom (Patent Literature 3); and thatpolymerization is conducted to some extent in the former reactor and asolvent is added to the latter reactor to conduct polymerization (PatentLiterature 4). In such apparatuses, however, removal of heat from areaction system is conducted by reflux cooling (a raw material monomeror the like in the reactor is evaporated to be taken out of the reactor,and it is returned to the reactor again after subjected to coldcondensation). Especially, in a case of conducting the polymerization ina less amount of solvent or with a high polymerization ratio in order toincrease a productivity, a viscosity of a mixture in the reaction systembecomes high, this makes the local or rapid cooling of the reactionsystem arise more easily, which makes the adhering and growing of thegel on the inner surface of the reactor prominent. As a result, there isa problem such as that gelled substance is immixed into a resultantpolymer composition as impurities. On the other hand, as to a continuoussolution polymerization process, a process is proposed which uses twostages of reactors, and set an average residence time in these reactorswithin the range given based on a half-life of a polymerizationinitiator (Patent Literature 5). In such apparatuses used in thisprocess, however, removal of heat from a reaction system is conducted byusing a jacket provided to an outer surface of the reactor. Especially,in a case of conducting the polymerization in a less amount of solventor with a high polymerization ratio in order to increase a productivity,the local or rapid cooling by using the jacket provided to an outersurface of the second reactor is required for maintaining temperature inthe first reactor and the second reactor at the same temperature toincrease polymerization ratio in the second reactor, which makesadhering and growing of the gel on an inner surface of the reactor. As aresult, the problem that gelled substance is immixed into a polymercomposition as impurities cannot be solved, and quality of a resultantresin is not always sufficient. The inventors have considered earnestlyon a novel continuous polymerization apparatus which can moreefficiently produce a polymer composition suitable for producing a resincomposition with high quality, and finally completed the presentinvention.

The present invention provides the following [1] to [9].

[1] A continuous polymerization apparatus which comprises, at least, afirst reactor and a second reactor which are of a complete mixing type,

wherein each of the reactors is provided with a supply port, an effluentport, and a temperature detecting means for detecting a temperature inthe reactor,

the supply port of the first reactor is connected to supply sources of araw material monomer and a polymerization initiator,

the effluent port of the first reactor is connected through a connectionline provided with a cooling means to the supply port of the secondreactor.

[2] The continuous polymerization apparatus according to the above [1],wherein the connection line is further provided with a mixing means.

[3] The continuous polymerization apparatus according to the above [1]or [2], wherein the effluent port of each of the reactors is placed atthe top of the reactor.

[4] The continuous polymerization apparatus according to any one of theabove [1]-[3], wherein the supply port of the second reactor or anothersupply port provided to the second reactor is connected to a supplysource of an additional polymerization initiator.

[5] The continuous polymerization apparatus according to any one of theabove [1]-[4], wherein the first reactor and the second reactor are usedfor conducting a continuous bulk polymerization.

[6] A process for producing a polymer composition by using thecontinuous polymerization apparatus according to any one of the above[1]-[5] which comprises:

a first polymerization step of continuously supplying a raw materialmonomer and a polymerization initiator from the supply sources of theraw material monomer and the polymerization initiator to the firstreactor though the supply port of the first reactor to be subjected tocontinuous polymerization in the first reactor, and continuously takinga resultant intermediate composition from the effluent port of the firstreactor,

an intermediate cooling step of continuously cooling the intermediatecomposition by the cooling means of the connection line during transportof the intermediate composition from the effluent port of the firstreactor to the supply port of the second reactor through the connectionline, and

a second polymerization step of continuously supplying the cooledintermediate composition to the second reactor through the supply portof the second reactor to be further subjected to continuouspolymerization in the second reactor, and continuously taking aresultant polymer composition from the effluent port of the secondreactor.

[7] The process for producing a polymer composition according to theabove [6], wherein a temperature of the intermediate composition in thesupply port of the second reactor is 5-80° C. lower than a temperatureof the intermediate composition in the effluent port of the firstreactor.

[8] The process for producing a polymer composition according to theabove [6] or [7], wherein a temperature in the first reactor detected bythe temperature detecting means of the first reactor and a temperaturein the second reactor detected by the temperature detecting means of thesecond reactor are within the range of 120-150° C.

[9] A molded article which is prepared from the polymer compositionproduced by the process according to any one of the above [6]-[8].

According to the present invention, there is provided a novel continuouspolymerization apparatus. Additionally, according to the presentinvention, there is provided a process for producing a polymercomposition wherein the process can be conducted by using suchcontinuous polymerization apparatus and more efficiently produce thepolymer composition suitable for obtaining a resin composition with highquality.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic view of a continuous polymerization apparatusin one embodiment of the present invention.

FIG. 2 shows a schematic view of a continuous polymerization apparatusin which a cooler is provided to the connection line in the embodimentof FIG. 1.

Following reference signs denote the following elements:

1 raw material monomer tank (supply source of raw material monomer)

3 polymerization initiator tank (supply source of polymerizationinitiator and, if necessary, of raw material monomer)

5 pump

7 pump

9 raw material supply line

10 first reactor

11 a supply port

11 b effluent port

11 c another supply port

13 jacket (temperature regulating means)

14 stirrer

15 connection line

16 jacket (cooling means)

17 polymerization initiator tank (supply source of additionalpolymerization initiator and, if necessary, of raw material monomer)

19 pump

20 second reactor

21 a supply port

21 b effluent port

21 c another supply port

23 jacket (temperature regulating means)

24 stirrer

25 effluent line

31 preheater

33 devolatilizing extruder

35 discharge line

37 recovery tank

40 cooler (cooling means)

T temperature sensor (temperature detecting means)

DESCRIPTION OF EMBODIMENTS

A continuous polymerization apparatus of the present invention comprisesat least two reactors, and continuous polymerization such as any ofcontinuous bulk polymerization and continuous solution polymerization isconducted in each of the reactors. The continuous polymerizationapparatus of the present invention will be understood as a continuousbulk polymerization apparatus when continuous bulk polymerization isconducted in all of reactors, and understood as a continuous solutionpolymerization apparatus when continuous solution polymerization isconducted in all of the reactors. However, the continuous polymerizationapparatus of the present invention is not limited thereto, but may bethose wherein continuous bulk polymerization is conducted in one reactor(e.g. at least one former reactor) and continuous solutionpolymerization is conducted in another reactor (e.g. at least one latterreactor).

Hereinafter, one embodiment of the present invention will be describedin detail with reference to FIG. 1.

A continuous polymerization apparatus in this embodiment comprises, atleast, a first reactor 10 and a second reactor 20. These reactors 10 and20 are both a reactor of a complete mixing type, and used to conductcontinuous bulk polymerization in this embodiment.

More specifically, the first reactor 10 is provided with a supply port11 a and an effluent port 11 b, and preferably further provided with ajacket 13 as a temperature regulating means for regulating a temperatureof an outer surface of the reactor and a stirrer 14 for stirringcontents therein. Similarly, the second reactor 20 is provided with asupply port 21 a and an effluent port 21 b, and preferably furtherprovided with a jacket 23 surrounding an outer surface of the reactor asa temperature regulating means for regulating a temperature of the outersurface of the reactor and a stirrer 24 for stirring contents therein.The effluent ports 11 b and 21 b are located at a top of each of thereactors in this embodiment, but not limited thereto. On the other hand,the supply ports 11 a and 21 a may be generally located at anappropriate position of a lower part of each of the reactors, althoughthis embodiment is not limited thereto. Each of these reactors 10 and 20may be provided with a temperature sensor T as a temperature detectingmeans for detecting a temperature in the reactor.

The first reactor 10 and the second reactor 20 may have the same ordifferent inner volume from each other. Making the inner volume of thefirst reactor and the inner volume of the second reactor different fromeach other, it is possible to effectively differentiate between thefirst reactor 10 and the second reactor 20 in an average residence time.

The stirrers 14 and 24 are a member for substantially attaining acomplete mixing condition in the reactors. These stirrers may have anyappropriate stirring blade(s), for example, may have blades of MIGimpeller, MAXBLEND impeller (registered trademark, manufactured bySumitomo Heavy Industries, Ltd.), paddle impeller, double helical ribbonimpeller, FULLZONE impeller (registered trademark, manufactured byKobelco Eco-Solutions Co., Ltd.) and so on. In order to increasestirring effect in the reactor, it is preferable to provide the reactorwith a baffle(s). However, this embodiment is not limited thereto, butmay have any appropriate configuration in place of the stirrers 14 and24 as long as a complete mixing condition can be substantially attainedin the reactors.

In general, the reactors 10 and 20 are more preferable when they have ahigher stirring efficiency. However, in view of avoiding the reactorsfrom being added with an unnecessary amount of heat by the stirringoperation, it is preferable that a power of stirring is not more thannecessary. The power of stirring is not particularly limited, butpreferably 0.5 to 20 kW/m³, and more preferably 1 to 15 kW/m³. As aviscosity of the reaction system becomes higher (or a content ratio of apolymer in the reaction system becomes higher), it is preferable to setthe power of stirring at a larger level.

As shown in the drawings, the supply port 11 a of the first reactor 10is connected through a raw material supply line 9 to a raw materialmonomer tank (a supply source of a raw material monomer) 1 and apolymerization initiator tank (a supply source of a polymerizationinitiator and, if necessary, of a raw material monomer) 3 via pumps 5and 7, respectively. In this embodiment, the supply sources of the rawmaterial monomer and the polymerization initiator are the raw materialmonomer tank 1 and the polymerization initiator tank 3, respectively.However, the number of the supply sources of the raw material monomerand the polymerization initiator, the forms of the raw material monomerand the polymerization initiator (in a case of a mixture, for example, acomposition thereof) and so on are not particularly limited as long asthe raw material monomer and the polymerization initiator can besupplied to the first reactor 10, appropriately. Although it is notnecessary for this embodiment, but another supply port 11 c may beprovided to the first reactor 10 and this supply port 11 c may beconnected to the polymerization initiator tank 3 via the pump 7 as shownby a dotted line in FIG. 1. The effluent port 11 b of the first reactor10 is connected to the supply port 21 a of the second reactor 20 througha connection line 15. The effluent port 21 b of the second reactor 20 islinked up to an effluent line 25. Thus, the first reactor 10 and thesecond reactor 20 are connected in series. There is preferably no pumpon the connection line 15 between the effluent port 11 b of the firstreactor 10 and the supply port 21 a of the second reactor 20.

It is not necessary for the present invention, but the second reactor 20is preferably connected to a polymerization initiator tank (a supplysource of an additional polymerization initiator and, if necessary, of araw material monomer) 17 via a pump 19. In this embodiment, the supplysource(s) of the additional polymerization initiator is thepolymerization initiator tank 17, but the number of the supply source(s)of the additional polymerization initiator, the form of thepolymerization initiator (in a case of a mixture, for example, acomposition thereof) and so on are not particularly limited as long asthe additional polymerization initiator can be supplied to the secondreactor 20, appropriately. In a case where the polymerization initiatortank 17 and the pump 19 are present, the supply port 21 a of the secondreactor 20 may be connected to the polymerization initiator tank 17 viathe pump 19 through the connection line 15 as shown in FIG. 1, or thesecond reactor 20 may be provided with another supply port 21 c so thatthis supply port 21 c is connected to the polymerization initiator tank17 via the pump 19 as shown by, for example, a dotted line in FIG. 1.

The pumps 5 and 7 and, if present, the pump 19 are not particularlylimited, but preferably pumps being able to set flow rates from the rawmaterial monomer tank 1 and the polymerization initiator tank 3 and aflow rate from the polymerization initiator tank 17, if present, atconstant values. More specifically, multiple reciprocating pumps arepreferred, and more preferred are pulsation-free controlled-volume pumpssuch as a duplicate pulsation-free controlled-volume pump and a triplexpulsation-free controlled-volume pump. By using these, it is possible tocontrol a supply amount (or a supply flow rate, which also applieshereinafter) of the raw material monomer and the polymerizationinitiator to the first reactor 10 and, if necessary, an additionalsupply amount of the polymerization initiator (or the raw materialmonomer and the polymerization initiator) to the second reactor 20.

Further, the connection line 15 which connects the effluent port 11 b ofthe first reactor 10 to the supply port 21 a of the second reactor 20 isprovided with, for example, a jacket 16 (shown by hatching in FIG. 1)surrounding a part of or the whole of an outer surface of the connectionline 15, a cooler 40 with which a part of the connection line 15 isreplaced as shown in FIG. 2, and/or a trace pipe through which a coolingmedium pass (the connection line provided with the jacket is understoodas a double pipe), as a cooling means being able to cool, at leastpartially, the connection line 15. Thereby, depending on the temperatureof the first reactor 10 and/or the second reactor 20 and so on, thetemperature of the connection line 15 (more specifically, thetemperature in the inside of the connection line) can be more lower. Asmentioned above, since the first reactor 10 is provided with thetemperature sensor T as a temperature detecting means for detecting atemperature in the first reactor 10, the jacket 16 or the cooler 40 (acooling means) of the connection line 15 can be controlled so that thetemperature in the connection line 15 adjacent to the supply port 21 aof the second reactor 20 is lower than the temperature in the firstreactor 10 which is detected by the temperature sensor T. In FIG. 2, thecooler 40 is provided to the connection line 15 in any appropriateconfiguration, and the line parts other than the cooler 40 of theconnection line 15 may be covered with a lagging to retain heat (notshown in the drawings), or a jacket (not shown in FIG. 2) surrounding anouter surface of the connection line 15 may be used in combination forcooling.

Further, it is not necessary for this embodiment, but the connectionline 15 is preferably provided with a mixing means in that a temperaturedistribution in the connection line 15 can be more homogenized, and anocclusion of the connection line 15 by an intermediate composition(hereinafter described) which flows through in the connection line 15can be suppressed. The mixing means is preferably provided to a coolingpart of the connection line 15 in view of enhancing a coolingefficiency. Examples of the mixing means include, for example, a staticmixer, a dynamic mixer, and so on. Among them, the static mixer ispreferable. The static mixer is a mixer without a drive member, and isprovided to the connection line 15 in any appropriate configuration. Forexample, in FIG. 1, the static mixer may be inserted into the connectionline 15 at an appropriate position, or a part of or the whole of theconnection line 15 may be replaced with the static mixer constitutingthe line. In FIG. 2, the static mixer can be inserted into a line partother than the cooler 40 of the connection line 15 at an appropriateposition, or a part of or the whole of the line part other than thecooler 40 of the connection line 15 may be replaced with the staticmixer constituting the line. Examples of the static mixer include, forexample, “Sulzer mixer” (manufactured by Sulzer Chemtech Ltd.) and soon. For example, Sulzer mixer of SMX type, SMI type, SMV type, SMF type,or SMXL type can be used.

Further, in the embodiment shown in FIG. 2, a cooler which combines acooling means and a mixing means may be provided as the cooler 40.Examples of the cooler 40 which combines a cooling means and a mixingmeans include a cooler having a dynamic mixing function and a coolerhaving a static mixing function. Examples of the cooler having a dynamicmixing function include, for example, a screw mixer being able to cool acylinder and so on. Examples of the cooler having a static mixingfunction include, for example, a heat exchanger with a built-in staticmixer and so on. As the heat exchanger with a built-in static mixer,preferably, Sulzer mixer of SMR type (manufactured by Sulzer ChemtechLtd.) is used in view of having a large a heat-transfer area and beingable to provide a high cooling capacity. In a case where the heatexchanger with a built-in static mixer is used as the cooler 40, a partof or the whole of the connection line 15 may be replaced with the heatexchanger with a built-in static mixer constituting the line.

It is preferable that each of the members described in the above withreference to FIG. 1 is appropriately connected to a control meansdescribed below (not shown in the drawings) and construct the whole soas to enable the control means to control their operations. Thereby, inorder to make the temperature of the outer surface of the reactor setfor each of the jackets (temperature regulating means) 13 and 23correspond to the temperature in the reactor detected by the temperaturesensor (temperature detecting means) T with respect to each of the firstreactor 10 and the second reactor 20 (in the other words, in order toachieve an adiabatic condition in each of the first reactor 10 and thesecond reactor 20), the supply amounts of the raw material monomer andthe polymerization initiator to the first reactor 10 can be adjusted bythe operation of the pumps 5 and 7, or the temperature of the outersurface of the reactor set for the jackets 13 and 23 can be regulated;and also, in a case where the polymerization initiator tank 17 and thepump 19 are present, the additional supply amount of the polymerizationinitiator (or the raw material monomer and the polymerization initiator)to the second reactor 20 can be adjusted by the operation of the pump19. Further, in order to achieve the desired polymerization ratio in thesecond reactor 20 and avoid a polymerization temperature in the secondreactor 20 from being too high, it is possible to make the temperaturein the connection line 15 adjacent to the supply port 21 a of the secondreactor 20 lower than the temperature in the first reactor 10 detectedby the temperature sensor (temperature detecting means) T by adjustingthe temperature of the outer surface of the connection line 15 set forthe jacket (cooling means) 16 covering the connection line 15. In FIG.2, the temperature in the connection line 15 adjacent to the supply port21 a of the second reactor 20 can become lower than the temperature inthe first reactor 10 detected by the temperature sensor (temperaturedetecting means) T by adjusting a setting temperature of the cooler 40with which a part of the connection line 15 is replaced. It ispreferable that the temperature in the connection line 15 is actuallymeasured at a place adjacent to the supply port 21 a of the secondreactor 20, or as the case may be, at other place by a temperaturedetecting means for detecting the temperature in the connection line 15.However, in some cases, depending on the polymerization reactionconditions in the first reactor 10, due to some causes such as that allof the supplied polymerization initiator is spent, an intermediatecomposition (hereinafter described) taken from the effluent port 11 bdoes not let the polymerization reaction proceed in the connection line15, that is, no heat of the polymerization reaction is generated in theconnection line 15. In such case, considering the temperature in theconnection line 15 adjacent to the effluent port 11 b of the firstreactor 10 as a substantially same temperature as the temperature in thefirst reactor 10 detected by the temperature sensor (temperaturedetecting means) T is allowable. Further, in such case, it is consideredthat the temperature in the connection line 15 adjacent to the supplyport 21 a of the second reactor 20 becomes lower than the temperature ofthe first reactor 10 by setting the temperature of the jacket 16covering the connection line 15 or the temperature of the cooler 40 withwhich a part of the connection line 15 is replaced at a temperaturelower than the temperature in the first reactor 10. In FIG. 2, when theline part other than the cooler 40 of the connection line 15 is providedwith a jacket surrounding it, the temperature in the connection line 15may be adjusted by using the jacket in combination.

The jackets 13 and 23 surround almost the whole of the reactors 10 and20, respectively to appropriately heat or retain the heat of thereactors 10 and 20 by introducing steam, hot water, organic heat mediumor the like from a heat medium supply route (not shown in the drawings).The temperature of the jackets 13 and 23 is able to be appropriatelyregulated with a temperature or pressure of the heat medium to beintroduced. The heat medium introduced into the jackets 13 and 23 isremoved from a heat medium discharge route (not shown in the drawings).The temperature and/or pressure of the jackets 13 and 23 are detected bya sensor such as a temperature sensor (not shown in the drawings)located on the heat medium discharge route. The point of location of asensor such as the temperature sensor is not particularly limited, butit may be located, for example, on the heat medium supply route, or inthe jackets 13 and 23. The jacket 16 provided to the connection line 15as a cooling means may have the same constitution as that of the jackets13 and 23. Although this embodiment is not limited thereto, theconnection line 15 may be typically a double pipe, in which the internalspace of the inner pipe is a flow path of an intermediate composition(hereinafter described), the space between the inner pipe and the outerpipe is a flow path of a heat medium (jacket 16).

For the polymerization reaction in the reactors 10 and 20, it isrequired to proceed at a generally constant temperature in each of thereactors 10 and 20 in view of obtaining a polymer with a constantquality. Therefore, the above described temperature regulating means(jackets 13 and 23) is controlled at a constant temperature which hasbeen set beforehand, so that the temperature inside the reactors 10 and20 can be maintained respectively at a generally constant temperature.

The setting temperature of the above described temperature regulatingmeans (jackets 13 and 23) is transmitted to a control means describedbelow, to be used as data for determining whether control of the supplyflow rate with the monomer supply means (pump 5) and/or the initiatorsupply means (pump 7 and, if present, pump 19) is necessary or not. Thesetting temperature of the above described temperature regulating means(jackets 13 and 23) can be regulated by controlling the temperature orpressure of the above described heat medium.

Examples of the control means include, for example, a control unit (notshown in the drawings) provided with CPU, ROM, RAM and so on.

The ROM of the control means is a device for storing a program whichcontrols the pumps 5 and 7 and, if present, the pump 19 and so on. TheRAM of the control means is a device for temporary storing data of thetemperatures in the reactors 10 and 20 detected by the temperaturesensor T, data of the setting temperatures of the jackets 13 and 23, anddata of the setting temperature of the jacket 16 or the cooler 40 of theconnection line 15 and so on in order to execute the above program.

The CPU of the control means executes the program stored in the ROMbased on data such as the data of the temperatures in the reactors 10and 20 and the data of the setting temperatures of the jackets 13 and 23stored in the above RAM so that the supply flow rates of the rawmaterial monomer and/or the polymerization initiator to the reactors 10and 20 is controlled by the monomer supply means (pump 5) and/or theinitiator supply means (pump 7 and, if present, pump 19). With respectto the jacket 16 or the cooler 40 provided to the connection line 15 asa cooling means, the CPU of the control means executes the programstored in the ROM (which may be either a part of the above program orother program than the above program) based on data such as the data ofthe temperatures in the reactors 10 and 20 and the data of the settingtemperature of the jacket 16 or the cooler 40 of the connection line 15stored in the above RAM, and in the case of actually measuring, thetemperature in the connection line 15 at the point adjacent to thesupply port 21 a of the second reactor 20 or other point, so that thesetting temperature of the jacket or the cooler 40 of the connectionline 15 can be adjusted.

An example of the control by the control means (control unit) will bedescribed below.

When the temperature in the reactor 10 detected by the temperaturesensor T exceeds the setting temperature of the jacket 13 as thetemperature regulating means, the CPU executes the program in the ROM tocontrol, for example, the pump 7 so as to decrease the supply flow rateof the polymerization initiator into the reactor 10. In a case where thepolymerization initiator tank 17 and the pump 19 are present, when thetemperature in the reactor 20 detected by the temperature sensor Texceeds the setting temperature of the jacket 23 as the temperatureregulating means during the pump 19 supplies the polymerizationinitiator to the reactor 20 to conduct the polymerization, the CPUexecutes the program in the ROM to control, for example, the pump 19 soas to decrease the supply flow rate of the polymerization initiator intothe reactor 20. By conducting such control, polymerization heatgenerated in the reactors 10 and/or 20 can be decreased, and thereby thetemperatures in the reactors 10 and/or 20 can be lowered.

On the other hand, when the temperature in the reactor 10 is below thesetting temperature of the jacket 13, the CPU executes the program inthe ROM to control, for example, the pump 7 so as to increase the supplyflow rate of the polymerization initiator into the reactor 10. In a casewhere the polymerization initiator tank 17 and the pump 19 are present,when the temperature in the reactor 20 is below the setting temperatureof the jacket 23 during the pump 19 supplies the polymerizationinitiator to the reactor 20 to conduct the polymerization, the CPUexecutes the program in the ROM to control, for example, the pump 19 soas to increase the supply flow rate of the polymerization initiator intothe reactor 20. By conducting such control, polymerization heatgenerated in the reactors 10 and/or 20 can be increased, and thereby thetemperatures in the reactors 10 and/or 20 can be raised.

For example, when the control over the pump 7 and, if present, the pump19 for the polymerization reaction in the reactors 10 and 20 results inremarkable decrease in the total supply flow rate into the reactors 10and 20, it is preferable to not only control the pump 7 and, if present,the pump 19 so as to decrease the supply flow rate of the polymerizationinitiator, but also to control the pump 5 so as to increase the supplyflow rate of the raw material monomer at the same time.

Further, as another example of the control, the following control isnoted. That is, when the temperature in the reactor 10 detected by thetemperature sensor T exceeds the setting temperature of the jacket 13 asthe temperature regulating means, the pump 5 is controlled to increasethe supply flow rate of the raw material monomer, so that the relativesupply flow rate of the polymerization initiator into the reactor 10 isdecreased. By conducting such control, the temperature in the reactor 10can also be lowered.

A ratio of the supply flow rate of the raw material monomer and thesupply flow rate of the polymerization initiator can be appropriatelyset depending on the kind of the polymer generated, the kind of thepolymerization initiator used, and so on.

Also, degree of increase or decrease in the supply flow rate of the rawmaterial monomer and/or the supply flow rate of the polymerizationinitiator can be appropriately set depending on the kind of the polymergenerated, the kind of the polymerization initiator used, and so on.However, in a case what is supplied to the reactors 10 and 20 by theinitiator supply means is not the polymerization initiator only, but theraw material monomer comprising the polymerization initiator, it isnecessary to consider a content ratio of the polymerization initiator inthe raw material monomer comprising polymerization initiator to controlthe supply flow rate of the polymerization initiator.

Further, as another example of the control, for the jacket 16 or thecooler 40 which is provided to the connection line 15 as a coolingmeans, the following control is noted. When the temperature in theconnection line 15 adjacent to the supply port 21 a of the secondreactor 20 is the temperature in the first reactor 10 detected by thetemperature sensor T or above, the CPU executes the program in the ROMto control a equipment associated with the jacket 16 or the cooler 40(not shown in the drawings) so as to adjust a setting temperature of thejacket 16 or the cooler 40 of the connection line 15 at a lowertemperature, so that the temperature in the connection line 15 adjacentto the supply port 21 a of the second reactor 20 become a lowertemperature, preferably 5-80° C. lower temperature, than the temperaturein the first reactor 10. The setting temperature of the jacket 16 of theconnection line 15 can generally be adjustable by controlling a flowrate and/or temperature of a heat medium flowed in the jacket 16, butnot particularly limited thereto. The setting temperature of the cooler40 of the connection line 15 can generally be adjustable, when a heatexchanger with a built-in static mixer is used as the cooler 40, bycontrolling a flow rate and/or temperature of a heat medium flowed inthe heat exchanger with a built-in static mixer, but not particularlylimited thereto.

As a preferable example of the control, the following control can beconducted. When the temperature in the second reactor 20 detected by thetemperature sensor T of the second reactor 20 is the temperature infirst reactor detected by the temperature sensor T of the first reactor10 or above, the CPU executes the program in the ROM to appropriatelycontrol as mentioned above so as to adjust the setting temperature ofthe jacket 16 or the cooler 40 (and, when the cooler 40 and a jacket areused in combination, the jacket) of the connection line 15, so that thetemperature in the connection line 15 adjacent to the supply port 21 aof the second reactor 20 become a lower temperature, preferably 5-80° C.lower temperature, than the temperature in the first reactor 10; or tocontrol the pumps 5 and 7 and, if present, the pump 19 so as to adjustthe flow rate to the reactor 10 and/or the reactor 20. Thereby thetemperature difference between the temperature in the first reactor 10and the temperature of the second reactor 20 can be reduced. When apolymerization heat is generated in the second reactor 20, for example,due to the presence of the polymerization initiator tank 17 and the pump19, it is effective to adjust the setting temperature of the jacket 16or the cooler 40 (and, when the cooler 40 and a jacket are used incombination, the jacket) of the connection line 15.

Additionally, it is not necessary for this embodiment, but a preheater31 and a devolatilizing extruder 33 may be located downstream of theeffluent line 25. There may be a pressure adjusting valve (not shown inthe drawings) provided between the preheater 31 and the devolatilizingextruder 33. An extruded object after devolatilization is dischargedfrom a discharge line 35.

As the preheater 31, any appropriate heater can be used as long as it isable to heat a viscous fluid. As the devolatilizing extruder 33, asingle or multi screw devolatilizing extruder can be used.

Further, there may be a recovery tank 37 for storing the raw materialmonomer which is separated and recovered from a volatile component(comprising unreacted raw material, mainly) separated with thedevolatilizing extruder 33.

Next, a process for producing a polymer composition conducted by usingsuch apparatus will be described. In this embodiment, a case ofconducting continuous polymerization of a methacrylic ester monomer, inthe other words, a case of producing a methacrylic ester polymer will bedescribed as an example, although the present invention is not limitedthereto.

Preparation

At first, the raw material monomer, the polymerization initiator and soon are prepared.

As the raw material monomer, a methacrylic ester monomer is used in thisembodiment.

Examples of the methacrylic ester monomer are

-   -   alkyl methacrylate (of which alkyl group has 1 to 4 carbons)        alone, or    -   a mixture of not less than 80% by weight of alkyl methacrylate        (of which alkyl group has 1 to 4 carbons) and not more than 20%        by weight of other vinyl monomer copolymerizable therewith.

Examples of alkyl methacrylate (of which alkyl group has 1 to 4 carbons)include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate,isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate,sec-butyl methacrylate, isobutyl methacrylate, and so on. Among them,methyl methacrylate is preferred. The above described examples of alkylmethacrylate may be used alone or in combination of at least two ofthem.

Examples of copolymerizable vinyl monomer include monofunctionalmonomers having one double bond which is radical-polymerizable andmultifunctional monomers having two or more double bonds which areradical-polymerizable. More specifically, examples of the monofunctionalmonomers having one double bond which is radical-polymerizable include,for example, methacrylic esters such as benzyl methacrylate and2-ethylhexyl methacrylate (except for the above described alkylmethacrylate (of which alkyl group has 1 to 4 carbons)); acrylic esterssuch as methyl acrylate, ethyl acrylate, propyl acrylate, butylacrylate, and 2-ethylhexyl acrylate; unsaturated carboxylic acids oracid anhydrides thereof such as acrylic acid, methacrylic acid, maleicacid, itaconic acid, maleic acid anhydride, and itaconic acid anhydride;hydroxy group-containing monomers such as 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, monoglycerol acrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, and monoglycerolmethacrylate; nitrogen-containing monomers such as acrylamide,methacrylamide, acrylonitrile, methacrylonitrile, diacetoneacrylamide,and dimethylaminoethyl methacrylate; epoxy group-containing monomerssuch as allyl glycidyl ether, glycidyl acrylate, and glycidylmethacrylate; styrene based monomers such as styrene andα-methylstyrene. Examples of the multifunctional monomers having two ormore double bonds which are radical-polymerizable include, for example,diesters of unsaturated carboxylic acids and glycols such as ethyleneglycol dimethacrylate, and butane diol dimethacrylate; unsaturatedcarboxylic acid alkenyl esters such as allyl acrylate, allylmethacrylate, and allyl cinnamate; polybasic acid polyalkenyl esterssuch as diallyl phthalate, diallyl maleate, triallyl cyanurate, andtriallyl isocyanurate; esters of unsaturated carboxylic acids andpolyalcohols such as trimethylolpropane triacrylate; and divinylbenzene.The above described examples of copolymerizable vinyl monomer may beused alone or in combination of at least two of them.

As the polymerization initiator, for example, radical initiator is usedin this embodiment.

Examples of the radical initiator include azo compounds such asazobisisobutyronitrile, azobisdimethylvaleronitrile,azobiscyclohexanenitrile, 1,1′-azobis(1-acetoxy-1-phenylethane),dimethyl 2,2′-azobisisobutylate, and 4,4′-azobis-4-cyanovaleric acid;organic peroxides such as benzoyl peroxide, lauroyl peroxide, acetylperoxide, caprylyl peroxide, 2,4-dichlorobenzoyl peroxide, isobutylperoxide, acetyl cyclohexylsulfonyl peroxide, t-butyl peroxypivalate,t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-butylperoxy-2-ethylhexanoate, 1,1-di(t-butylperoxy)cyclohexane,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, isopropylperoxydicarbonate, isobutyl peroxydicarbonate, s-butylperoxydicarbonate, n-butyl peroxydicarbonate, 2-ethylhexylperoxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, t-amylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethyl butylperoxy-ethylhexanoate, 1,1,2-trimethyl propyl peroxy-2-ethylhexanoate,t-butyl peroxy isopropyl monocarbonate, t-amyl peroxy isopropylmonocarbonate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxyallyl carbonate, t-butyl peroxy isopropyl carbonate, 1,1,3,3-tetramethylbutyl peroxy isopropyl monocarbonate, 1,1,2-trimethyl propyl peroxyisopropyl monocarbonate, 1,1,3,3-tetramethyl butyl peroxy isononate,1,1,2-trimethyl propyl peroxy-isononate, and t-butyl peroxybenzoate.

These polymerization initiators may be used alone or in combination ofat least two of them.

The polymerization initiator is selected depending on the kinds of thepolymer to be produced and the raw material monomer used. For example,although the present invention is not particularly limited, as thepolymerization initiator (radical initiator), those of which τ/θ (−) is,for example not more than 0.1, preferably not more than 0.02, morepreferably not more than 0.01 can be used, wherein τ (second) representsa half-life of the polymerization initiator at the polymerizationtemperature, and θ (second) represents an average residence time in areactor. When the value of τ/θ is not more than the above value, apolymerization reaction can be effectively initiated because thepolymerization initiator is sufficiently decomposed (thus, generating aradical) in a reactor. Further, since the polymerization initiator issufficiently decomposed in the first reactor 10, it can be effectivelysuppressed to decompose the polymerization initiator to initiatepolymerization in the connection line 15, as a result, it can beeffectively avoided to increase a viscosity of the intermediatecomposition during it passes through the connection line 15, and/or toocclude the connection line 15 by the intermediate composition.

The supply amount of the polymerization initiator (radical initiator) isnot particularly limited, but generally 0.001 to 1% by weight withrespect to the raw material monomer (the raw material monomer eventuallysupplied to the reactor 10). In a case where the polymerizationinitiator tank 17 and the pump 19 are present in addition to thepolymerization initiator tank 3 and the pump 7, the polymerizationinitiator can be supplied separately into the first reactor 10 and thesecond reactor 20. When the polymerization initiator tank 17 suppliesthe mixture of the raw material monomer and the polymerization initiatorto the second reactor 20 by the pump 19, the total supply amount of thepolymerization initiator supplied to the reactor 10 and the reactor 20is made within the above range with respect to the sum of the rawmaterial monomer eventually supplied to the reactor 10 and the rawmaterial monomer additionally supplied to the reactor 20.

In addition to the raw material monomer and the polymerization initiatordescribed above, any appropriate other component(s), for example, achain transfer agent, a mold release agent, a rubbery polymer such asbutadiene and styrene-butadiene rubber (SBR), a thermal stabilizingagent, and an ultraviolet absorbing agent may be used. The chaintransfer agent is used for adjusting a molecular weight of a producedpolymer. The mold release agent is used for improving moldability (orprocessability) of a resin composition obtained from the polymercomposition. The thermal stabilizing agent is used for preventing aproduced polymer from thermal degradation. The ultraviolet absorbingagent is used for preventing a produced polymer from being degraded byultraviolet rays.

As to the chain transfer agent, either monofunctional or polyfunctionalchain transfer agent can be used. More specifically, examples thereofinclude alkyl mercaptans such as n-propyl mercaptan, isopropylmercaptan, n-butyl mercaptan, t-butyl mercaptan, n-hexyl mercaptan,n-octyl mercaptan, 2-ethylhexyl mercaptan, n-dodecyl mercaptan, andt-dodecyl mercaptan; aromatic mercaptans such as phenyl mercaptan andthiocresol; mercaptans having 18 or less carbons such as ethylenethioglycol; polyalcohols such as ethylene glycol, neopentyl glycol,trimethylolpropane, pentaerythritol, dipentaerythritol,tripentaerythritol, and sorbitol; those of which hydroxyl group isesterified with thioglycolic acid or 3-mercaptopropionic acid,1,4-dihydronaphthalene, 1,4,5,8-tetrahydronaphthalene,β-terpinene,terpinolene, 1,4-cyclohexadiene, hydrogen sulfide and so on. These maybe used alone or in combination of at least two of them.

The supply amount of the chain transfer agent is not particularlylimited since it varies depending on the kind of the chain transferagent used and so on. For example, in a case of using mercaptans, it ispreferably 0.01 to 3% by weight, and more preferably 0.05 to 1% byweight with respect to the raw material monomer (the raw materialmonomer eventually supplied to the reactor 10).

Examples of the mold release agents are not particularly limited, butinclude esters of higher fatty acids, higher fatty alcohols, higherfatty acids, higher fatty acid amides, metal salts of higher fatty acidsand so on. As the mold release agent, one or more kinds thereof may beused.

Examples of the esters of higher fatty acids specifically include, forexample, saturated fatty acid alkyl esters such as methyl laurate, ethyllaurate, propyl laurate, butyl laurate, octyl laurate, methyl palmitate,ethyl palmitate, propyl palmitate, butyl palmitate, octyl palmitate,methyl stearate, ethyl stearate, propyl stearate, butyl stearate, octylstearate, stearyl stearate, myristyl myristate, methyl behenate, ethylbehenate, propyl behenate, butyl behenate, octyl behenate; unsaturatedfatty acid alkyl esters such as methyl oleate, ethyl oleate, propyloleate, butyl oleate, octyl oleate, methyl linoleate, ethyl linoleate,propyl linoleate, butyl linoleate, octyl linoleate; saturated fatty acidglycerides such as lauric monoglyceride, lauric diglyceride, laurictriglyceride, palmitic monoglyceride, palmitic diglyceride, palmitictriglyceride, stearic monoglyceride, stearic diglyceride, stearictriglyceride, behenic monoglyceride, behenic diglyceride, behenictriglyceride; unsaturated fatty acid glycerides such as oleicmonoglyceride, oleic diglyceride, oleic triglyceride, linolicmonoglyceride, linolic diglyceride, linolic triglyceride. Among them,methyl stearate, ethyl stearate, butyl stearate, octyl stearate, stearicmonoglyceride, stearic diglyceride, stearic triglyceride, and son on arepreferred.

Examples of the higher fatty alcohols specifically include, for example,saturated fatty (or, aliphatic) alcohols such as lauryl alcohol,palmityl alcohol, stearyl alcohol, isostearyl alcohol, behenyl alcohol,myristyl alcohol, cetyl alcohol; unsaturated fatty (or aliphatic)alcohols such as oleyl alcohol, linolyl alcohol. Among them, stearylalcohol is preferred.

Examples of the higher fatty acids specifically include, for example,saturated fatty acids such as caproic acid, caprylic acid, capric acid,lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid,behenic acid, lignoceric acid, 12-hydroxyoctadecanoic acid; unsaturatedfatty acids such as palmitoleic acid, oleic acid, linoleic acid,linolenic acid, cetoleic acid, erucic acid, ricinoleic acid.

Examples of the higher fatty acid amides specifically include, forexample, saturated fatty acid amides such as lauric acid amide, palmiticacid amide, stearic acid amide, behenic acid amide; unsaturated fattyacid amides such as oleic acid amide, linoleic acid amide, erucic acidamide; amides such as ethylene-bis-lauric acid amide,ethylene-bis-palmitic acid amide, ethylene-bis-stearic acid amide,N-oleyl stearamide. Among them, stearic acid amide andethylene-bis-stearic acid amide are preferred.

Examples of the metal salts of higher fatty acids include, for example,sodium salts, potassium salts, calcium salts and barium salts of theabove-described higher fatty acids, and so on.

A used amount of the mold release agent is preferably adjusted in arange from 0.01 to 1.0 part by weight, and more preferably adjusted in arange from 0.01 to 0.50 part by weight, with respect to 100 parts byweight of a polymer contained in a polymer composition to be obtained.

Examples of the thermal stabilizing agent are not particularly limited,but include, for example, phosphorous-based thermal stabilizing agentand organic disulfide compounds. Among them, the organic disulfidecompounds are preferable. As the thermal stabilizing agent, one or morekinds thereof may be used.

Examples of the phosphorus-based thermal stabilizing agent include, forexample, tris(2,4-di-t-butylphenyl)phosphite,2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepine-6-yl]oxy]-N,N-bis[2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepine-6-yl]oxy]-ethyl]ethanamine,diphenyl tridecyl phosphite, triphenyl phosphite,2,2-methylenebis(4,6-di-tert-butylphenyl)octylphosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, and soon. Among them, 2,2-methylenebis(4,6-di-tert-butylphenyl)octylphosphiteis preferred.

Examples of the organic disulfide compounds include, for example,dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, di-n-butyldisulfide, di-sec-butyl disulfide, di-tert-butyl disulfide, di-tert-amyldisulfide, dicyclohexyl disulfide, di-tert-octyl disulfide, di-n-dodecyldisulfide, di-tert-dodecyl disulfide, and so on. Among them,di-tert-alkyl disulfide is preferred, and di-tert-dodecyl disulfide ismore preferred.

A used amount of the thermal stabilizing agent is preferably 1-2,000 ppmby weight with respect to a polymer contained in a polymer compositionto be obtained. On molding a polymer composition (more specifically, aresin composition after devolatilization) to prepare a molded articlefrom the polymer composition of the present invention, a moldingtemperature is set at a higher temperature for the purpose of improvingits molding processability in some cases. Use of the thermal stabilizingagent is effective for such case.

As the kinds of the ultraviolet absorbing agent, a benzophenone-basedultraviolet absorbing agent, a cyanoacrylate-based ultraviolet absorbingagent, a benzotriazole-based ultraviolet absorbing agent, a malonicester-based ultraviolet absorbing agent, an oxalic anilide-basedultraviolet absorbing agent and so on are exemplified. These ultravioletabsorbing agents may be used alone or in combination of at least two ofthem. Among them, the benzotriazole-based ultraviolet absorbing agent,the malonic ester-based ultraviolet absorbing agent, and the oxalicanilide-based ultraviolet absorbing agent are preferable.

Examples of the benzophenone-based ultraviolet absorbing agent include,for example, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2-hydroxy-4-methoxybenzophenone-5-sulfonic acid,2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone,4-benzyloxy-2-hydroxybenzophenone,2,2′-dihydroxy-4,4′-dimethoxybenzophenone, and so on.

Examples of the cyanoacrylate-based ultraviolet absorbing agent include,for example, ethyl 2-cyano-3,3-diphenylacrylate, 2-ethylhexyl2-cyano-3,3-diphenylacrylate, and so on.

Examples of the benzotriazole-based ultraviolet absorbing agent include,for example, 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole,5-chloro-2-(3,5-di-tert-butyl-2-hydroxyphenyl)-2H-benzotriazole,2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole,2-(3,5-di-tert-pentyl-2-hydroxyphenyl)-2H-benzotriazole,2-(3,5-di-tert-butyl-2-hydroxyphenyl)-2H-benzotriazole,2-(2H-benzotriazole-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenol,2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole, and so on.

As to the malonic ester-based ultraviolet absorbing agent, 2-(1-arylalkylidene)malonates are generally used, and examples thereof includedimethyl 2-(p-methoxybenzylidene)malonate and so on.

As to the oxalic anilide-based ultraviolet absorbing agent,2-alkoxy-2′-alkyloxalic anilides are generally used, and examplesthereof include 2-ethoxy-2′-ethyloxalic anilide and so on.

A used amount of the ultraviolet absorbing agent is preferably 5-1,000ppm by weight with respect to a polymer contained in a polymercomposition to be obtained.

In the raw material monomer tank 1, the raw material monomer (one kindor a mixture of two or more kinds) as described above is appropriatelyprepared (together with other component(s) such as the chain transferagent as the case may be). In the polymerization initiator tank 3, thepolymerization initiator as described above is appropriately preparedwith the raw material monomer if necessary (together with othercomponent(s) such as the chain transfer agent as the case may be). Thepolymerization initiator tank 3 may store the polymerization initiatoralone or in the form of the mixture of the raw material monomer and thepolymerization initiator (may further comprise other component(s) suchas the chain transfer agent as the case may be). In a case of using thepolymerization initiator tank 17, in the polymerization initiator tank17, the polymerization initiator as described above is appropriatelyprepared with the raw material monomer if necessary (together with othercomponent(s) such as the chain transfer agent as the case may be). Thepolymerization initiator tank 17 may store the polymerization initiatoralone or in the form of the mixture of the raw material monomer and thepolymerization initiator (may further comprise other component(s) suchas the chain transfer agent as the case may be). However, in a casewhere the polymerization initiator tank 17 is connected to the supplyport 21 c via the pump 19, storing of the polymerization initiator aloneraises a concern of local proceeding of the polymerization reaction inthe reactor 20 since the polymerization initiator is solely supplied tothe reactor 20. On the contrary, storing in the form of the mixture ofthe raw material monomer and the polymerization initiator is able tosolve such concern since the polymerization initiator is mixed with apart of the raw material monomer beforehand.

First Polymerization Step

The raw material monomer and the polymerization initiator arecontinuously supplied to the first reactor 10 through the supply port 11a from the raw material monomer tank 1 and the polymerization initiatortank 3 as the supply source(s) of the raw material monomer and thepolymerization initiator. More specifically, the raw material monomer iscontinuously supplied from the raw material monomer tank 1 by the pump5, and the polymerization initiator (preferably, the mixture of the rawmaterial monomer and the polymerization initiator, which is also simplyreferred to as the polymerization initiator herein) is supplied from thepolymerization initiator tank 3 by the pump 7, and they merge togetherthrough the raw material supply line 9 into the first reactor 10 via thesupply port 11 a. Also, the polymerization initiator may be suppliedfrom the polymerization initiator tank 3 by the pump 7 to the firstreactor 10 via the supply port 11 c as shown by the dotted line in FIG.1.

For supplying the polymerization initiator to the first reactor 10, whenthe mixture of the raw material monomer and the polymerization initiatoris prepared in the polymerization initiator tank 3 and suppliedtherefrom, it is preferable to adjust a ratio A:B in a range from 80:20to 98:2 wherein A represents the supply flow rate (kg/h) of the rawmaterial monomer from the raw material monomer tank 1, and B representsthe supply flow rate (kg/h) of the mixture of the raw material monomerand the polymerization initiator (of which content ratio of thepolymerization initiator is 0.002 to 10% by weight) from thepolymerization initiator tank 3.

The temperature of the raw material monomer and the polymerizationinitiator supplied to the first reactor 10 is not particularly limited.However, this is one of factors which may change the polymerizationtemperature by losing a heat balance in the reactor, and therefore it ispreferable to adjust that temperature appropriately by a heater/cooler(not shown in the drawings) before the supply to the reactor 10.

The raw material monomer and the polymerization initiator supplied tothe first reactor 10 as described in the above are subjected tocontinuous polymerization, continuous bulk polymerization in thisembodiment (in other words, polymerization with no solvent). This firstpolymerization step has only to proceed the polymerization reactionpartway, and an intermediate composition is continuously taken from theeffluent port 11 b of the first reactor 10.

In the first polymerization step, the continuous polymerization can beconducted under a condition in which the reactor is filled with thereaction mixture while substantially no gas phase is present(hereinafter referred to as a fully filled condition). This isespecially suitable for the continuous bulk polymerization. The fullyfilled condition can prevent beforehand the problems such as that geladheres to and grows on the inner surface of the reactor, and that thisgel is immixed into the reaction mixture to degrade quality of a polymercomposition obtained in the end. Further, the fully filled conditionenables all of the inner volume of the reactor to be used as a reactionspace, and thereby a high productivity can be attained.

By locating the effluent port 11 b of the first reactor 10 at thereactor's top as in this embodiment, the fully filled condition isconveniently realized simply by conducting the supply to and the takingfrom the first reactor 10, continuously. It is suitable for continuouspolymerization of a methacrylic ester monomer that the effluent port islocated at the reactor's top.

Further in the first polymerization step, the continuous polymerizationmay be conducted under the adiabatic condition (condition withsubstantially no heat transfer to or from outside of the reactor). Thisis especially suitable for the continuous bulk polymerization. Theadiabatic condition can prevent beforehand the problems such as that geladheres to and grows on the inner surface of the reactor, and that thisgel is immixed into the reaction mixture to degrade quality of a polymercomposition obtained in the end. Further, the adiabatic conditionenables the polymerization reaction to become stable, and selfregulating characteristics for suppressing a runaway reaction can bebrought about.

The adiabatic condition can be realized by making the temperature of theinside of the first reactor 10 and the temperature of the outer surfacethereof generally equal to each other. More specifically, this can berealized, with the use of the above described control means (not shownin the drawings), by adjusting the supply amounts of the raw materialmonomer and the polymerization initiator to the first reactor 10 withoperating the pumps 5 and 7 such that the temperature of the outersurface of the first reactor 10 set for the jacket (temperatureregulating means) 13 and the temperature in the first reactor 10detected by the temperature sensor (temperature detecting means) Tcorrespond to each other. It is not preferable to set the temperature ofthe outer surface of the reactor much higher than the temperature in thereactor since it adds extra amount of heat into the reactor. The smallerthe difference between the temperature in the reactor and thetemperature of the outer surface of the reactor is, the better it is.More specifically, it is preferable to adjust the temperature differencewithin the range of ±5° C.

The heat generated in the first reactor 10 such as polymerization heatand stirring heat is generally carried away on taking the intermediatecomposition from the first reactor 10. The amount of the heat carriedaway by the intermediate composition is determined by the flow rate andthe specific heat of the intermediate composition, and the temperatureof the polymerization reaction.

The temperature of the continuous polymerization in the firstpolymerization step is understood as the temperature in the firstreactor 10 (detected by the temperature sensor T). The firstpolymerization step is conducted, for example, at a temperature in therange of 120 to 150° C., more preferably at a temperature in the rangeof 130 to 150° C. It is noted, however, that the temperature in thereactor may change according to various conditions until it reaches astatic state.

The pressure of the continuous polymerization in the firstpolymerization step is understood as the pressure in the first reactor10. This pressure is a pressure not less than a vapor pressure of theraw material monomer at the temperature in the reactor to prevent gas ofthe raw material monomer from generating in the reactor, and isgenerally about 1.0 to 2.0 MPa in gauge pressure.

A time period subjected to the continuous polymerization in the firstpolymerization step is understood as an average residence time in thefirst reactor 10. The average residence time in the first reactor 10 canbe set according to the productivity of the polymer in the intermediatecomposition and so on, and is not particularly limited, but, forexample, from 15 minutes to 6 hours. The average residence time in thefirst reactor 10 can be adjusted by using the pumps 5 and 7 to changethe supply amount (supply flow rate) of the raw material monomer or thelike to the first reactor 10. However, since the average residence timedepends in a large part on the inner volume of the first reactor 10, howthe inner volume of the first reactor 10 and the inner volume of thesecond reactor 20 are designed is important as hereinafter described.

As described in the above, the intermediate composition is continuouslytaken from the effluent port 11 b of the first reactor 10. The obtainedintermediate composition comprises the generated polymer and theunreacted raw material monomer, and may further comprise the unreactedpolymerization initiator, decomposed substance of the polymerizationinitiator, and so on.

Although this embodiment is not limited thereto, the polymerizationratio in the intermediate composition is, for example, 5 to 80% byweight. The polymerization ratio in the intermediate compositiongenerally corresponds to the content ratio of the polymer in theintermediate composition.

Intermediate Cooling Step

The intermediate composition obtained as described in the above is takenfrom the effluent port 11 b of the first reactor 10, followed by passingthrough the connection line 15 and supplied to the second reactor 20through the supply port 21 a, continuously. During this time, theintermediate composition is continuously cooled by the jacket 16 or thecooler 40 which is a cooling means provided to the connection line 15.

Further, it is not necessary for the present invention, but it ispreferable to provide the connection line 15 with a mixing means. Byproviding with the mixing means, the intermediate composition flowing inthe connection line 15 is homogeneously mixed. As a result, atemperature distribution tends to be homogenized, and an occlusion ofthe connection line 15 by the intermediate composition can besuppressed. When the connection line 15 is provided with the mixingmeans, the connection line 15 may be provided with a static mixer or adynamic mixer, or the connection line 15 may be provided with the cooler40 which combines a mixing means and a cooling means.

Degree of cooling may be varied depending on difference between thetemperature in the first reactor 10 and the temperature in the secondreactor 20, and so on, for example, as in the preferable example of thecontrol described in the above. The degree of cooling is adjusteddepending on the desired polymerization temperature and polymerizationratio in the second reactor 20, specifically, the cooling can beconducted so that the temperature of the intermediate composition in thesupply port 21 a of the second reactor 20 become, for example, 5 to 80°C. lower temperature than the temperature of the intermediatecomposition in the effluent port 11 b of the first reactor 10.

Second Polymerization Step

The second polymerization step is conducted in series with and followingto the first polymerization step.

After the intermediate composition cooled by being passed through theconnection line 15 as described in the above is supplied to the secondreactor 20 from the supply port 21 a. Then, the intermediate compositionis further subjected to continuous polymerization, continuous bulkpolymerization in this embodiment in the second reactor 20. This secondpolymerization step is to let the polymerization reaction proceed to thedesired polymerization ratio, and a polymer composition (orpolymerization syrup) is continuously taken from the effluent port 21 bof the second reactor 20.

Hereinafter, the second polymerization step will be described mainlywith respect to different points from the first polymerization step, andexplanations similar to those for the first polymerization step applyunless otherwise explained.

Although it is not necessary to this embodiment, but it is preferable touse the polymerization initiator tank 17 and the pump 19. In a case ofusing the polymerization initiator tank 17 and the pump 19, theadditional (or fresh) polymerization initiator (preferably, the mixtureof the raw material monomer and the polymerization initiator) issupplied from the polymerization initiator tank 17 by the pump 19through the connection line 15 to the second reactor 20 via the supplyport 21 a or the another supply port 21 c, and thereby the additionalpolymerization initiator is added to the intermediate composition. Thetemperature of the polymerization initiator supplied to the secondreactor 20 from the polymerization initiator tank 17 is not particularlylimited. However, this is one of factors which may change in thepolymerization temperature by losing a heat balance in the reactor, andtherefore it is preferable to appropriately adjust the temperature by aheater/cooler (not shown in the drawings) before the supply to thereactor 20.

Further, cooling the intermediate composition taken from the firstreactor by using the jacket 16 or the cooler 40 which is provided to theconnection line 15 as a cooling means before supplying it to the secondreactor, even if a polymerization heat is generated in the secondreactor 20, it is possible to conduct continuous polymerization withavoiding generation of a temperature inhomogeneous state in the secondreactor 20, and to achieve a high polymerization ratio with retain a lowtemperature in the second reactor 20, that is, to increase aproductivity of the polymer. As a result, it is possible to effectivelyproduce the polymer composition having superior thermal stability andheat resistance. Further, keeping a supply temperature of theintermediate composition to the second reactor 20 constant by adjustingthe supply temperature by using the jacket 16 or the cooler 40 which isprovided to the connection line 15 as a cooling means, it is possible tomore stably conduct continuous polymerization in the secondpolymerization step.

For supplying the polymerization initiator to the second reactor 20,when the mixture of the raw material monomer and the polymerizationinitiator is prepared in the polymerization initiator tanks 3 and 17 andsupplied therefrom, it is preferable to adjust a ratio A:(B1+B2) in arange from 80:20 to 98:2 and a ratio B1:B2 in a range from 10:90 to90:10 wherein A represents the supply flow rate (kg/h) of the rawmaterial monomer from the raw material monomer tank 1, B1 represents thesupply flow rate (kg/h) of the mixture of the raw material monomer andthe polymerization initiator (of which content ratio of thepolymerization initiator is 0.002 to 10% by weight) from thepolymerization initiator tank 3, and B2 represents a supply flow rate(kg/h) of the mixture of the raw material monomer and the polymerizationinitiator (of which content ratio of the polymerization initiator is0.002 to 10% by weight) from the polymerization initiator tank 17.

Also, in the second polymerization step, the continuous polymerizationcan be conducted under a fully filled condition. This is especiallysuitable for the continuous bulk polymerization. The fully filledcondition can prevent beforehand the problems such as that gel adheresto and grows on the inner surface of the reactor, and that this gel isimmixed into the reaction mixture to degrade quality of the polymercomposition obtained in the end. Further, the fully filled conditionenables all of the inner volume of the reactor to be used as a reactionspace, and thereby a high productivity can be attained.

By locating the effluent port 21 b of the second reactor 20 at thereactor's top as in this embodiment, the fully filled condition isconveniently realized simply by continuously conducting the supply toand the taking from the second reactor 20, continuously. It is suitablefor continuous polymerization of a methacrylic ester monomer that theeffluent port is located at the reactor's top.

Also, further in the second polymerization step, the continuouspolymerization may be conducted under the adiabatic condition. This isespecially suitable for the continuous bulk polymerization. Theadiabatic condition can prevent beforehand the problems such as that geladheres to and grows on the inner surface of the reactor, and that thisgel is immixed into the reaction mixture to degrade quality of thepolymer composition obtained in the end. Further, the adiabaticcondition enables the polymerization reaction to become stable, and selfregulating characteristics for suppressing a runaway reaction can bebrought about.

The adiabatic condition can be realized by making the temperature of theinside of the second reactor 20 and the temperature of the outer surfacethereof generally equal to each other. More specifically, this can berealized, with the use of the above described control means (not shownin the drawings), by adjusting the supply amounts of the raw materialmonomer and the polymerization initiator to the second reactor 20 withoperating the pumps 5 and 7 and, if present, the pump 19 such that thetemperature of the outer surface of the second reactor 20 set for thejacket (temperature regulating means) 23 and the temperature in thesecond reactor 20 detected by the temperature sensor (temperaturedetecting means) T correspond to each other. It is not preferable to setthe temperature of the outer surface of the reactor much higher than thetemperature in the reactor since it adds extra amount of heat into thereactor. The smaller the difference between the temperature in thereactor and the temperature of the outer surface of the reactor is, thebetter it is. More specifically, it is preferable to adjust thetemperature difference within the range of ±5° C.

The heat generated in the second reactor 20 such as polymerization heatand stirring heat is generally carried away on taking the polymercomposition from the second reactor 20. The amount of the heat carriedaway by the polymer composition is determined by the flow rate and thespecific heat of the polymer composition, and the temperature of thepolymerization reaction.

The temperature of the continuous polymerization in the secondpolymerization step is understood as the temperature in the secondreactor 20. The second polymerization step is conducted, for example, ata temperature in the range of 120 to 150° C., more preferably at atemperature in the range of 130 to 150° C. It is preferable to adjustthe temperature in the second polymerization step so that temperaturedifference from the temperature of the continuous polymerization in thefirst polymerization step falls within 10° C. In the secondpolymerization step, though the temperature may be increased bypolymerization heat generated in the polymerization reaction, it ispossible to reduce difference between the temperature in the firstpolymerization step and the temperature in the second polymerizationstep by the intermediate cooling. As a result, the thermal stability andheat resistance is improved compared with when the polymerization isconducted at a lower temperature in the first reactor, then thepolymerization is conducted at a higher temperature in the secondreactor.

The pressure of the continuous polymerization in the secondpolymerization step is understood as the pressure in the second reactor20. This pressure is generally about 1.0 to 2.0 MPa in gauge pressure,and may be equal to the pressure in the first polymerization step.

A time period subjected to the continuous polymerization in the secondpolymerization step is understood as an average residence time in thesecond reactor 20. The average residence time in the second reactor 20can be set according to the productivity of the polymer in the polymercomposition and so on, and is not particularly limited, but, forexample, from 15 minutes to 6 hours. A ratio of the average residencetime in the second reactor 20 to the average residence time in the firstreactor 10 is preferably from 9/1 to 1/9, and more preferably from 8/2to 2/8. The average residence time in the second polymerization step maybe equal to the average residence time in the first polymerization step,but preferably different from it. The average residence time in thesecond reactor 20 can be adjusted by using the pumps 5 and 7 and, ifpresent, the pump 19 to change the supply amount (supply flow rate) ofthe raw material monomer or the like to the second reactor 20. However,since the average residence time depends in a large part on the innervolume of the second reactor 20, how the inner volume of the firstreactor 10 and the inner volume of the second reactor 20 are designed isimportant as hereinafter described.

As described in the above, the polymer composition is continuously takenfrom the effluent port 21 b of the second reactor 20. The obtainedpolymer composition comprises the generated polymer, and may furthercomprise the unreacted raw material monomer, the unreactedpolymerization initiator, decomposed substance of the polymerizationinitiator, and so on.

Although this embodiment is not limited thereto, the polymerizationratio in the polymer composition is, for example, 30 to 90% by weight.The polymerization ratio in the polymer composition generallycorresponds to the content ratio of the polymer in the polymercomposition. The higher the polymerization ratio, the higher theproductivity of the polymer, but also the higher the viscosity of thecomposition from intermediate composition to the polymer composition,resulting in the larger the necessary power for stirring. The lower thepolymerization ratio, the lower the productivity of the polymer,resulting in the larger the load for recovering the unreacted rawmaterial monomer. Therefore, it is preferable to set an appropriatepolymerization ratio as a target or a guide.

According to this embodiment, in order to achieve the desiredpolymerization ratio and low polymerization temperature in the secondreactor 20, simultaneously, the cooling means of the connection line iscontrolled so as to make the temperature in the connection line adjacentto the supply port of the second reactor lower than the temperature inthe first reactor detected by the temperature detecting means of thefirst reactor, thereby it is possible to produce the polymer compositionhaving superior thermal stability and heat resistance with highproductivity.

In general, the following tendency is observed: the higher thepolymerization temperature, the lower the syndiotacticity of theobtained polymer, the lower the heat resistance of a resin compositionobtained in the end. Therefore, it is preferable to conduct apolymerization at a low temperature to obtain a resin composition havinghigh heat resistance. However, if continuous polymerization is conductedin one stage only at a lower temperature with the use of theconventional continuous polymerization apparatus (Patent Literatures 1and 2), a long time is required to achieve the desired polymerizationratio. Therefore, it requires a larger reactor, furthermore larger spaceto realize a longer average residence time, so that it is not efficient.In addition, when the average residence time is longer than necessary,the generation of the oligomer such as a dimer and trimer is increased,thereby a concern of decreasing the heat resistance of the resinobtained from the polymer composition is raised.

In addition, the amount of the polymerization initiator can be setdepending on other factors such as a polymerization temperature, adesired polymerization ratio, and an average residence time, and so on.The lower the polymerization temperature or the shorter the averageresidence time, the larger the amount of the polymerization initiatorrequired for achieving the desired polymerization ratio. However, thelarger the amount of the polymerization initiator, the larger theremained amount of the terminal part which consists of a unstableunsaturated bond and at which polymerization is stopped (terminalpolymer) in the polymer composition, as a result, the thermal stabilityof the resin composition finally obtained tends to be decreased. Also,the much higher the polymerization temperature, the larger the generatedamount of the terminal part which consists of an unsaturated bondderived from the polymerization initiator and at which polymerization isstopped (terminal polymer) in the polymer composition, as a result, thethermal stability of the resin composition finally obtained tends to bedecreased.

In this embodiment, for example, the continuous polymerization isconducted at the temperature in the given range (for example, 120-150°C.) in the first polymerization step, then the continuous polymerizationcan be further conducted at the temperature in the same range as in thefirst polymerization step (for example, 120-150° C.) in the secondpolymerization step. Specifically, a cooling step is conducted in theconnection line between the first reactor and the second reactor andadditional polymerization initiator is supplied to the second reactor soas to reduce the difference between the temperature of the continuouspolymerization in the first polymerization step and the temperature ofthe continuous polymerization in the second polymerization step, andthen an adiabatic polymerization can be conducted. As a result, thecontinuous polymerization can be effectively conducted in the smallerspace compared with when it is conducted in one stage at a lowertemperature, and can produce the polymer composition suitable forobtaining a resin composition which has higher heat resistance andcontains lower impurities such as gel generated by an adiabaticpolymerization compared with when it is conducted in one stage at ahigher temperature.

Further, in this embodiment, for example, a time period subjected to thecontinuous polymerization in the first polymerization step can differfrom a time period subjected to the continuous polymerization in thesecond polymerization step. Specifically, it is possible todifferentiate between the first reactor and the second reactor in anaverage residence time by designing the reactors so as to make the innervolume of the first reactor and the inner volume of the second reactordifferent from each other. Further, it is possible to differentiatebetween the first reactor and the second reactor in an average residencetime by adding additional polymerization initiator together with the rawmaterial monomer to the second reactor. When the average residence timeis increased, by controlling the residence time and the polymerizationratio in the first reactor and the second reactor, it is possible todecrease the amount of the polymerization initiator to be supplied tothe reactor, thereby obtaining the polymer composition suitable forregulating the thermal stability of the whole of the resin compositionto obtain the resin composition having high thermal stability.

How the polymerization reaction conditions are set for each of the firstpolymerization step and the second polymerization step may varyaccording to the polymer generated, the raw material monomer and thepolymerization initiator used, the heat resistance, thermal stabilityand productivity desired, and so on.

Devolatilization Step

As described in the above, the polymer composition (polymerizationsyrup) taken from the effluent port 21 b of the second reactor 20 maycomprise the unreacted raw material monomer and polymerization initiatorand so on, in addition to the generated polymer. Although thisembodiment is not limited thereto, such polymer composition ispreferably subjected to, for example, devolatilization to separate andrecover the raw material monomer.

More specifically, the polymer composition is transferred to thepreheater 31 through the effluent line 25. The polymer composition inthe preheater 31 is added with a part or all of an amount of heatnecessary to volatilize the volatile component which is mainly composedof the unreacted raw material monomer. Then, the polymer composition istransferred to the devolatilizing extruder via the pressure adjustingvalve (not shown in the drawings), and the volatile component is atleast partially removed in the devolatilizing extruder, and a residualextruded object is formed into pellets and discharged from the dischargeline 35. Thereby, the resin composition comprising a methacrylic esterpolymer is produced in the form of the pellets.

As a method for transferring the above polymer composition, a methoddescribed in JP 4-48802 B is preferable. As a method of using adevolatilizing extrude, methods described in, for example, JP 3-49925 A,JP 51-29914 B, JP 52-17555 B, JP 1-53682 B, JP 62-89710 A and so on arepreferable.

Further, during or after devolatilization of the polymer composition inthe devolatilizing extruder described above, the polymer composition orthe extruded object can be added with lubricants such as higher alcoholsand higher fatty acid esters, an ultraviolet absorbing agent, a thermalstabilizing agent, colorant, an antistatic agent and so on, in order toincorporate them into the resin composition, if necessary.

The volatile component removed in the devolatilizing extruder 33consists primarily of the unreacted raw material monomer and includesimpurities; e.g. impurities originally contained in the raw materialmonomer, additives used if necessary, volatile by-product(s) generatedin the process of polymerization, oligomer such as dimer and trimer,decomposed substance of the polymerization initiator, and so on. Ingeneral, a larger amount of the impurities make the obtained resincomposition colored, which is not preferable. Then, the volatilecomponent removed in the devolatilizing extruder 33 (which consistsprimarily of the unreacted raw material monomer and includes impuritiesas described above) may be passed through a monomer recovery column (notshown in the drawings), and treated by means of distillation, adsorptionand so on in the monomer recovery column to remove the impurities fromthe above described volatile component. Thereby, the unreacted rawmaterial monomer can be recovered with high purity, so that it can besuitably reused as the raw material monomer for polymerization. Forexample, continuous distillation is conducted in the monomer recoverycolumn to recover the unreacted raw material monomer with high purity asa distillate liquid from the top of the monomer recovery column, and itmay be transferred and recycled to the raw material monomer tank 1 afterit is reserved in the recovery tank 37 once, or it may be transferredand recycled to the raw material monomer tank 1 without being reservedin the recovery tank 37. On the other hand, the impurities removed inthe monomer recovery column may be disposed as a waste.

In order to prevent the recovered raw material monomer from causing thepolymerization reaction in the recovery tank 37 and/or the raw materialmonomer tank 1, it is preferable that a polymerization inhibitor existsin the recovery tank 37 or the raw material monomer tank 1 at a ratioof, for example, 2 to 8 ppm by weight with respect to the raw materialmonomer, and more preferably, in addition to this, an oxygenconcentration in a gas phase in the recovery tank 37 or the raw materialmonomer tank 1 is set at 2 to 8% by volume. If the recovered rawmaterial monomer is wanted to be preserved in the recovery tank 37 for along time, it is preferable to reserve it at a low temperature of, forexample, 0 to 5° C.

In this embodiment, the continuous bulk polymerization apparatus whereinthe first reactor and the second reactor are both used to conduct thecontinuous bulk polymerization is described. However, the continuouspolymerization apparatus of the present invention is not limitedthereto, one or both of the first reactor and the second reactor may beused to conduct continuous solution polymerization. In such embodiment,since a solvent is used for the solution polymerization, the continuouspolymerization apparatus is provided, in addition to a similarconfiguration to the continuous polymerization apparatus described inthe above with reference to FIGS. 1-2, with a solvent tank and a supplyline and a pump (supply means) associated with the solvent tank tosupply the solvent to a certain reactor for conducting the solutionpolymerization. The solvent tank and the supply line and the pump(supply means) associated with the solvent tank are not particularlylimited, those similar to conventionally used ones can be used. Thesolvent can be supplied to the certain reactor for conducting thesolution polymerization after being mixed with the raw material monomerand/or the polymerization initiator, or can be supplied to the certainreactor for conducting the solution polymerization, directly. In theabove certain reactor, the polymerization step is conducted similarly tothe polymerization step described in the above with reference to FIGS.1-2, except that the solvent is used in the polymerization reaction. Asto the solvent, it is appropriately selected according to the rawmaterial monomer of the solution polymerization reaction and so on, andnot particularly limited, but examples thereof include toluene, xylene,ethyl benzene, methyl isobutyl ketone, methyl alcohol, ethyl alcohol,octane, decane, cyclohexane, decalin, butyl acetate, pentyl acetate, andso on. A ratio C:D is, for example, 70:30 to 95:5, and preferably 80:20to 90:10, but not limited thereto, wherein C represents a supply flowrate (kg/h) of the raw material monomer to the certain reactor forconducting the solution polymerization, and D represents a supply flowrate (kg/h) of the solvent to this certain reactor.

The continuous polymerization apparatus and the process for producingthe polymer composition of the present invention are hereinbeforedescribed through the embodiment of the present invention in detail.According to the present invention, provided is, a novel continuouspolymerization apparatus, and when such continuous polymerizationapparatus are used, since the polymerization can be conducted in atleast two stages in series by using at least the first reactor and thesecond reactor, it is possible to set the polymerization reactionconditions, specifically, the temperature, the time period (averageresidence time), the amount of the polymerization initiator (a ratio ofthe polymerization initiator to the raw material monomer) and so on ineach of the first polymerization step and the second polymerizationstep, respectively. Therefore, depending on the desired polymerizationtemperature and polymerization ratio in the second reactor, the coolingmeans of the connection line can be controlled to make the temperaturein the connection line adjacent to the supply port of the second reactorlower than the temperature in the first reactor detected by thetemperature detecting means of the first reactor, thereby it becomespossible to control the syndiotacticity of the polymer contained in thefinally obtained resin composition to more efficiently produce thepolymer composition suitable for obtaining a resin composition havinghigh heat resistance and thermal stability.

However, the present invention is not limited to the above embodiment,and various modifications can be made. For example, three or morereactors can be used to conduct the polymerization in three or morestages in series. Further, the process for producing the polymercomposition of the present invention is continuously conductedpreferably by using the continuous polymerization apparatus of thepresent invention, but it may be conducted in a batch method.

The polymer composition produced by the process of the present inventionis preferably used as a material for a molded article, and the moldedarticle obtained therefrom has an advantage of having high heatresistance and thermal stability. For example, the polymer compositionproduced by the process of the present invention (more specifically, theresin composition after devolatilization) is molded alone or togetherwith any suitable other component(s) according to any molding processsuch as injection molding and extrusion molding to prepare a moldedarticle. The polymer composition produced by the process of the presentinvention is preferably used for preparing a molded article by injectionmolding, and it is possible to prepare a molded article with goodmoldability and prevent silver streaks from occurring. Especially, sincethe resin composition comprising a methacrylic ester based polymer has asuperior transparency, the molded article prepared from it by injectionmolding has high transparency and less occurrence of silver streaks andgood moldability, and therefore it is preferably utilized as a materialfor a light guide plate, which is used as a member of a backlight unitfor various types of liquid crystal displays, or for vehicle memberssuch as a rear lamp cover, a head lamp cover, a visor, a meter panel,and so on.

Injection molding can be conducted by filling (injecting into) a moldhaving a certain thickness with at least the polymer compositionproduced by the process of the present invention in a molten state,followed by cooling, and then thus molded article is released from themold. More specifically, the molded article can be prepared by, forexample, supplying a molding machine from a hopper with the polymercomposition produced by the process of the present invention (morespecifically, the resin composition after devolatilization) alone or incombination with any other suitable components, retracting and rotatinga screw to measure the resin composition in a cylinder of the moldingmachine, melting the resin composition in the cylinder, filling a mold(e.g. metal mold) with the molten resin composition under pressure,holding the pressure for a certain time period until the mold issufficiently cooled, opening the mold to eject the molded articletherefrom.

Thus, according to another aspect of the present invention, there isalso provided a molded article prepared from the polymer compositionproduced by the process of the present invention. It is noted thatconditions for preparing the molded article of the present inventionfrom the polymer composition (for example, in a case of injectionmolding, a temperature for melting a molding material, a temperature ofa mold to which the molding material is injected, a pressure to be heldafter the mold is filled with the molding material, and so on) can beappropriately set and are not specifically limited.

EXAMPLES

Examples of the process for producing polymer composition of the presentinvention are shown below, though the present invention is not limitedto these Examples.

Example 1

In this Example, generally, continuous polymerization was conducted intwo stages according to the embodiment described above with reference toFIG. 1 to produce a polymer composition in the form of pellets (resincomposition). More specifically, this was as explained below.

A raw material monomer mixed liquid 1 was prepared by mixing 98.606parts by mass of methyl methacrylate and 0.987 part by mass of methylacrylate together, and adding thereto 0.284 part by mass of n-octylmercaptan as a chain transfer agent, and 0.123 part by mass of stearylalcohol as a mold release agent.

A polymerization initiator mixed liquid 1 was prepared by mixing 99.790parts by mass of methyl methacrylate, and 0.210 part by mass of t-amylperoxy-2-ethylhexanoate as a polymerization initiator.

A polymerization initiator mixed liquid 2 was prepared by mixing 99.880parts by mass of methyl methacrylate, and 0.120 part by mass of t-amylperoxy-2-ethylhexanoate as a polymerization initiator.

For producing a polymer composition in this Example, the apparatus shownin FIG. 1 was used. A reactor of a complete mixing type having acapacity of 13 litters was used as the first reactor 10, and a reactorof a complete mixing type having a capacity of 6 litters was used as thesecond reactor 20. The raw material monomer mixed liquid 1, thepolymerization initiator mixed liquid 1, and the polymerizationinitiator mixed liquid 2 as prepared above were charged to the rawmaterial monomer tank 1, the polymerization initiator tank 3, and thepolymerization initiator tank 17, respectively.

The raw material monomer mixed liquid 1 and the polymerization initiatormixed liquid 1 flowed through the raw material supply line 9respectively from the raw material monomer tank 1 and the polymerizationinitiator tank 3, and were continuously supplied to the first reactor 10through the supply port 11 a located at its lower part.

The supply of the raw material monomer mixed liquid 1 and thepolymerization initiator mixed liquid 1 to the first reactor 10 wasconducted so that a ratio of flow rates of them was 19.2:1 and anaverage residence time in the first reactor 10 was 64 minutes. Atemperature in the first reactor 10 was 140° C., and a temperature ofthe jacket 13 surrounding the outer surface of the first reactor 10 wasset at 140° C., so that the continuous polymerization was conductedunder an adiabatic condition with substantially no heat transfer. Thiscontinuous polymerization was conducted under a condition in which thefirst reactor 10 was filled with a reaction mixture (mixed liquid) andsubstantially no gas phase was present (fully filled condition). Ahalf-life (τ) of t-amyl peroxy-2-ethylhexanoate is 14 seconds at 140° C.

The reaction mixture in the first reactor 10 was continuously taken outas an intermediate composition from the effluent port 11 b located onthe top of the first reactor 10. The intermediate composition thus takenwas continuously flowed through the connection line 15 and supplied tothe second reactor 20 through the supply port 21 a located at its lowerpart. The connection line 15 was provided with the jacket 16 surroundingits outer surface. A temperature of this jacket 16 was set at 100° C. Atemperature in the connection line 15 adjacent to the supply port 21 aof the second reactor 20, in the other words, a temperature of theintermediate composition in the supply port 21 a of the second reactor20 was 105° C. Considering a temperature of the intermediate compositionin the effluent port 11 b of the first reactor 10 as the sametemperature in the first reactor 10, i.e. 140° C., is allowable. Inaddition, the polymerization initiator mixed liquid 2 was continuouslysupplied from the polymerization initiator tank 17 to the second reactor20 through the another supply port 21 c.

The supply of the intermediate composition and the polymerizationinitiator mixed liquid 2 to the second reactor 20 was conducted so thata ratio of flow rates of them was 24.7:1. An average residence time inthe second reactor 20 was 26 minutes. A temperature in the secondreactor 20 was 140° C., and a temperature of the jacket 23 surroundingthe outer surface of the second reactor 20 was set at 140° C., so thatthe continuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer. This continuous polymerization wasconducted under a condition in which the second reactor 20 was filledwith a reaction mixture (mixed liquid) and substantially no gas phasewas present (fully filled condition).

The reaction mixture in the second reactor 20 was continuously taken outas a polymer composition from the effluent port 21 b located on the topof the second reactor 20. The polymer composition thus obtained wascontinuously flowed through the effluent line 25 and heated in thepreheater 31 to 200° C., and a volatile component such as the unreactedraw material monomer was separated therefrom at 240° C. by thedevolatilizing extruder 33 equipped with a vent. A resin compositionobtained after devolatilization was extruded in a molten state, cooledwith water, and then cut into pellets which were discharged from thedischarge line 35. Thus, the resin composition was produced in the formof pellets. The conditions in this Example are shown in Table 1.

A polymerization ratio (wt %) was determined from the supply weights perhour of the raw material monomer mixed liquid 1, the polymerizationinitiator mixed liquid 1, and the polymerization initiator mixed liquid2, and the production (discharge) weight per hour of the pellets.Further, with respect to the produced pellets, thermal stability (wt %)and heat resistance (° C.) were evaluated, and reduced viscosity (cm³/g)was measured as explained below. Results of them are shown in Table 2.

<Thermal Stability>

Using a TG-DTA apparatus (“TG/DTA 6300” manufactured by SeikoInstruments Inc.), the pellets produced in the above were subjected totemperature rising from 50° C. to 500° C. with a rising temperature rateof 2° C./min under nitrogen flow of 200 mL/min, and change in its weightwas measured.

On the basis of the weight of the pellets at the point of 50° C., aweight loss therefrom was determined. Assuming that a rate of the weightloss was 100 wt % at the point of 500° C., a rate of the weight loss (wt%) from 260 to 300° C. was calculated.

The rate of the weight loss (wt %) from 260 to 300° C. representsthermal stability, showing that the smaller its value, the lesseroccurrence of thermal degradation starting from an unsaturated end, i.e.the better the thermal stability.

<Heat Resistance>

Using a DSC apparatus (“DSC6200” manufactured by Seiko InstrumentsInc.), according to the differential scanning calorimetry methodprovided in JIS K 7121, the pellets produced in the above were subjectedto temperature rising to 150° C. with a rising temperature rate of 20°C./min under nitrogen flow of 100 mL/min and held for 5 minutes, andthen subjected to temperature reduction to −50° C. with a fallingtemperature rate of 20° C./min and held for one minute. Then, they weresubjected to temperature rising from −50° C. to 215° C. with a risingtemperature rate of 10° C./min, and a mid-point glass transitiontemperature (Tmg) was determined. It shows that the larger its value,the higher the heat resistance.

<Reduced Viscosity>

In conformity with ISO 1628-6, 0.5 g of the pellets produced in theabove was dissolved in chloroform to prepare a solution of 50 cm³, itsviscosity was determined by Cannon-Fenske viscometer at 25° C.

Comparative Example 1

In this Comparative Example, generally, the polymer composition wasproduced without cooling in the connection line between the firstreactor and the second reactor. More specifically, the polymercomposition was produced in the form of pellets similarly to Example 1,except for the following points.

Similarly to Example 1, a raw material monomer mixed liquid 1 wasprepared by mixing 98.606 parts by mass of methyl methacrylate and 0.987part by mass of methyl acrylate together, and adding thereto 0.284 partby mass of n-octyl mercaptan as a chain transfer agent, and 0.123 partby mass of stearyl alcohol as a mold release agent.

Similarly to Example 1, a polymerization initiator mixed liquid 1 wasprepared by mixing 99.790 parts by mass of methyl methacrylate, and0.210 part by mass of t-amyl peroxy-2-ethylhexanoate as a polymerizationinitiator.

A polymerization initiator mixed liquid 2′ was prepared by mixing 99.860parts by mass of methyl methacrylate, and 0.140 part by mass of1,1-di(t-butylperoxy)cyclohexane as a polymerization initiator which isdifferent from the polymerization initiator in the polymerizationinitiator mixed liquid 2 in Example 1.

In this Comparative Example, a temperature in the first reactor 10 was140° C., and a temperature of the jacket 13 surrounding the outersurface of the first reactor 10 was set at 140° C., so that thecontinuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer (similarly to Example 1, a ratio offlow rates of the raw material monomer mixed liquid 1 and thepolymerization initiator mixed liquid 1 which were supplied to the firstreactor 10 was 19.2:1 and an average residence time in the first reactor10 was 64 minutes). A temperature of the jacket 16 of the connectionline 15 was set at 140° C. A temperature in the connection line 15adjacent to the supply port 21 a of the second reactor 20, in the otherwords, a temperature of the intermediate composition in the supply port21 a of the second reactor 20 was 140° C. Considering a temperature ofthe intermediate composition in the effluent port 11 b of the firstreactor 10 as the same temperature in the first reactor 10, i.e. 140°C., is allowable. In addition, a temperature in the second reactor 20was 175° C., and a temperature of the jacket 23 surrounding the outersurface of the second reactor 20 was set at 175° C., so that thecontinuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer (similarly to Example 1, a ratio offlow rates of the intermediate composition and the polymerizationinitiator mixed liquid 2′ which were supplied to the second reactor 20was 24.7:1 and an average residence time in the second reactor 20 was 26minutes). A half-life (τ) of 1,1-di(t-butylperoxy)cyclohexane is 7seconds at 175° C. The conditions in this Comparative Example are shownin Table 1.

Thus, the polymer composition was produced in the form of pellets (resincomposition). In this Comparative Example, similarly to Example 1, apolymerization ratio (wt %) was determined from the supply weights perhour of the raw material monomer mixed liquid 1, the polymerizationinitiator mixed liquid 1 and the polymerization initiator mixed liquid2′, and the production (discharge) weight per hour of the pellets.Further, similarly to Example 1, with respect to the produced pellets,thermal stability (wt %) and heat resistance (° C.) were evaluated, andreduced viscosity (cm³/g) was measured. Results of them are shown inTable 2.

Comparative Example 2

In this Comparative Example, generally, the polymer composition wasproduced without cooling in the connection line between the firstreactor and the second reactor and with adding a polymerizationinhibitor to the second reactor to inhibit the progress of thepolymerization reaction. More specifically, the polymer composition wasproduced in the form of pellets similarly to Example 1, except for thefollowing points.

Similarly to Example 1, a raw material monomer mixed liquid 1 wasprepared by mixing 98.606 parts by mass of methyl methacrylate and 0.987part by mass of methyl acrylate together, and adding thereto 0.284 partby mass of n-octyl mercaptan as a chain transfer agent, and 0.123 partby mass of stearyl alcohol as a mold release agent.

Approximately similarly to Example 1, a polymerization initiator mixedliquid 1 was prepared by mixing 99.801 parts by mass of methylmethacrylate, and 0.199 part by mass of t-amyl peroxy-2-ethylhexanoateas a polymerization initiator.

Differently from Example 1, the polymerization initiator mixed liquid 2was not used. Instead, a polymerization inhibitor mixed liquid 1 whichcomprises 2,4-dimethyl-6-t-butylphenol as a polymerization inhibitor inmethyl methacrylate at a concentration of 50 ppm by mass was prepared.

In this Comparative Example, a temperature in the first reactor 10 was140° C., and a temperature of the jacket 13 surrounding the outersurface of the first reactor 10 was set at 140° C., so that thecontinuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer (similarly to Example 1, a ratio offlow rates of the raw material monomer mixed liquid 1 and thepolymerization initiator mixed liquid 1 which were supplied to the firstreactor 10 was 19.2:1 and an average residence time in the first reactor10 was 64 minutes). A temperature of the jacket 16 of the connectionline 15 was set at 140° C. A temperature in the connection line 15adjacent to the supply port 21 a of the second reactor 20, in the otherwords, a temperature of the intermediate composition in the supply port21 a of the second reactor 20 was 140° C. Considering a temperature ofthe intermediate composition in the effluent port 11 b of the firstreactor 10 as the same temperature in the first reactor 10, i.e. 140°C., is allowable. In this Comparative Example, the polymerizationinhibitor mixed liquid 1 in place of the polymerization initiator mixedliquid 2 was stored in the polymerization initiator tank 17. Thepolymerization inhibitor mixed liquid 1 was continuously supplied fromthe polymerization initiator tank 17 to the second reactor 20 throughthe another supply port 21 c. The supply of the intermediate compositionand the polymerization inhibitor mixed liquid 1 to the second reactor 20was conducted so that a ratio of flow rates of them was 24.7:1. Inaddition, a temperature in the second reactor 20 was 140° C., and atemperature of the jacket 23 surrounding the outer surface of the secondreactor 20 was set at 140° C., so that the continuous polymerization wasconducted under an adiabatic condition with substantially no heattransfer (similarly to Example 1, an average residence time in thesecond reactor 20 was 26 minutes). The conditions in this ComparativeExample are shown in Table 1.

Thus, the polymer composition was produced in the form of pellets (resincomposition). In this Comparative Example, similarly to Example 1, apolymerization ratio (wt %) was determined from the supply weights perhour of the raw material monomer mixed liquid 1, the polymerizationinitiator mixed liquid 1 and the polymerization inhibitor mixed liquid1, and the production (discharge) weight per hour of the pellets.Further, similarly to Example 1, with respect to the produced pellets,thermal stability (wt %) and heat resistance (° C.) were evaluated, andreduced viscosity (cm³/g) was measured. Results of them are shown inTable 2.

TABLE 1 Comparative Comparative Example 1 Example 1 Example 2 FirstPolymerization 140 140 140 reactor temperature (° C.) Half-life of 14 1414 Polymerization initiator τ (sec) Average residence 64 × 60 64 × 60 64× 60 time θ (sec) τ/θ (—) 0.0036 0.0036 0.0036 Second Polymerization 140175 140 reactor temperature (° C.) Half-life of 14 7 — Polymerizationinitiator τ (sec) Average residence 26 × 60 26 × 60 26 × 60 time θ (sec)τ/θ (—) 0.0090 0.0045 — Temperature in the connection 105 140 140 line(° C.)

TABLE 2 Comparative Comparative Example 1 Example 1 Example 2Polymerization ratio 59 56 44 (wt %) Reduced viscosity 59.0 56.1 56.0(cm³/g) Thermal stability 2.2 2.9 1.8 (wt %) Heat resistance 117 115 116Tmg (° C.)

As understood from Table 2, Example 1 produced the polymer composition(resin composition) having the thermal stability and the heat resistancebetter than those of Comparative Example 1, while the polymerizationratio and the reduced viscosity giving an indication of a molecularweight of the polymer were retained at an equal level to those ofComparative Example 1. Further, though Comparative Example 2 producedthe polymer composition (resin composition) having the thermal stabilitybetter than that of Example 1, Example 1 produced the polymercomposition showing the polymerization ratio better than that ofComparative Example 2, that is, with high productivity, thus Example 1could more effectively produce the polymer composition (resincomposition).

Example 2

In this Example, generally, according to the embodiment described abovewith reference to FIG. 1, the continuous polymerization was conducted intwo stages to produce a polymer composition in the form of pellets(resin composition). Further, in order to evaluate its moldability, theproduced pellets were molded into a molded article. More specifically,this was as explained below.

A raw material monomer mixed liquid 2 was prepared by mixing 92.2605parts by mass of methyl methacrylate, 7.145 parts by mass of methylacrylate and 0.076 part by mass of ethylene glycol dimethacrylatetogether, and adding thereto 0.375 part by mass of n-octyl mercaptan asa chain transfer agent, 0.121 part by mass of stearic monoglyceride and0.013 part by mass of methyl stearate as mold release agents, 0.0005part by mass of di-tert-dodecyl disulfide as a thermal stabilizingagent, and 0.009 part by mass of dimethyl2-(p-methoxybenzylidene)malonate as an ultraviolet absorbing agent.

A polymerization initiator mixed liquid 3 was prepared by mixing 99.725parts by mass of methyl methacrylate, and 0.275 part by mass of t-amylperoxy-2-ethylhexanoate as a polymerization initiator.

A polymerization initiator mixed liquid 4 was prepared by mixing 89.099parts by mass of methyl methacrylate and 10.8 parts by mass of methylacrylate, and 0.101 part by mass of t-amyl peroxy-2-ethylhexanoate as apolymerization initiator.

For producing a polymer composition in this Example, the apparatus shownin FIG. 1 was used. A reactor of a complete mixing type having acapacity of 13 litters was used as the first reactor 10, and a reactorof a complete mixing type having a capacity of 6 litters was used as thesecond reactor 20. The raw material monomer mixed liquid 2, thepolymerization initiator mixed liquid 3, and the polymerizationinitiator mixed liquid 4 as prepared above were charged to the rawmaterial monomer tank 1, the polymerization initiator tank 3, and thepolymerization initiator tank 17, respectively.

The raw material monomer mixed liquid 2 and the polymerization initiatormixed liquid 3 flowed through the raw material supply line 9respectively from the raw material monomer tank 1 and the polymerizationinitiator tank 3, and were continuously supplied to the first reactor 10through the supply port 11 a located at its lower part.

The supply of the raw material monomer mixed liquid 2 and thepolymerization initiator mixed liquid 3 to the first reactor 10 wasconducted so that a ratio of flow rates of them was 16.7:1 and anaverage residence time in the first reactor 10 was 46 minutes. Atemperature in the first reactor 10 was 140° C., and a temperature ofthe jacket 13 surrounding the outer surface of the first reactor 10 wasset at 140° C., so that the continuous polymerization was conductedunder an adiabatic condition with substantially no heat transfer. Thiscontinuous polymerization was conducted under a condition in which thefirst reactor 10 was filled with a reaction mixture (mixed liquid) andsubstantially no gas phase was present (fully filled condition).

The reaction mixture in the first reactor 10 was continuously taken outas an intermediate composition from the effluent port 11 b located onthe top of the first reactor 10. The intermediate composition thus takenwas continuously flowed through the connection line 15 and supplied tothe second reactor 20 through the supply port 21 a located at its lowerpart. The connection line 15 was provided with the jacket surroundingits outer surface. This jacket 16 was used to be set at 100° C. Atemperature in the connection line 15 adjacent to the supply port 21 aof the second reactor 20, in the other words, a temperature of theintermediate composition in the supply port 21 a of the second reactor20 was 105° C. Considering a temperature of the intermediate compositionin the effluent port 11 b of the first reactor 10 as the sametemperature in the first reactor 10, i.e. 140° C., is allowable. Inaddition, the polymerization initiator mixed liquid 4 was continuouslysupplied from the polymerization initiator tank 17 to the second reactor20 through the another supply port 21 c.

The supply of the intermediate composition and the polymerizationinitiator mixed liquid 4 to the second reactor 20 was conducted so thata ratio of flow rates of them was 18.3:1. An average residence time inthe second reactor 20 was 19 minutes. A temperature in the secondreactor 20 was 140° C., and a temperature of the jacket 23 surroundingthe outer surface of the second reactor 20 was set at 140° C., so thatthe continuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer. This continuous polymerization wasconducted under a condition in which the second reactor 20 was filledwith a reaction mixture (mixed liquid) and substantially no gas phasewas present (fully filled condition).

The reaction mixture in the second reactor 20 was continuously taken outas a polymer composition from the effluent port 21 b located on the topof the second reactor 20. The polymer composition thus obtained wascontinuously flowed through the effluent line 25 and heated in thepreheater 31 to 200° C., and a volatile component such as the unreactedraw material monomer was separated therefrom at 240° C. by thedevolatilizing extruder 33 equipped with a vent. A resin compositionobtained after devolatilization was extruded in a molten state, cooledwith water, and then cut into pellets which were discharged from thedischarge line 35. Thus, the resin composition was produced in the formof pellets. The conditions in this Example are shown in Table 3.

A polymerization rate (wt %) was determined from the supply weights perhour of the raw material monomer mixed liquid 2, the polymerizationinitiator mixed liquid 3, and the polymerization initiator mixed liquid4, and the production (discharge) weight per hour of the pellets.Further, with respect to the produced pellets, MFR (melt mass flow rate)and moldability were evaluated as explained below. Results of them areshown in Table 4.

<MFR>

In conformity with JIS K 7210, with respect to the produced pellets, MFRwas measured at 230° C. under a load of 37.3 N.

<Moldability>

The pellets produced in the above were supplied from a hopper to amolding machine set at a certain cylinder temperature, and injectionmolding was repeatedly conducted through the cylinder in this moldingmachine, thereby molded articles were prepared in sequence. Conditionsfor the injection molding are shown in below. After the cylindertemperature became stable, ten molded articles in sequence obtained bysequential ten shots (cycles) of injection molding were taken assamples, and a silver streaks occurrence ratio was determined bycounting samples showing occurrence of silver streaks among these tensamples. More specifically, the molded articles were subjected to visualobservation, and occurrence of silver streaks was recognized when silverstreaks was observed in the molded article. The silver streaksoccurrence ratio were determined for three different cylindertemperatures according to the similar procedures.

Metal Mold:

-   -   Rectangle of 23 cm×30.5 cm (plane view), thickness of 0.8 mm    -   One fan gate (located on a longitudinal side of the rectangle in        the plane)    -   Gate width 304 mm

Molding Machine:

-   -   Electric servo drive injection molding machine (“J450ELIII-890H”        manufactured by The Japan Steel Works, LTD.)

Cylinder Temperature:

-   -   300° C., 305° C., 310° C. at a nozzle head temperature (molding        temperature)

Hopper Side Temperature:

-   -   220° C.

Molding Conditions:

Injection pressure 179 MPa Injection speed 160 mm/sec Metal moldtemperature 80° C. Injection time period 0.4 sec Back pressure 15 MPaScrew rotation speed 45 rpm Holding pressure 45 MPa Holding pressuretime 11 sec

Molding Cycle:

-   -   100 sec (including cooling time of 70 sec)

Residence Time in Cylinder:

-   -   12 min

Comparative Example 3

In this Comparative Example, generally, the polymer composition wasproduced without cooling in the connection line between the firstreactor and the second reactor. More specifically, the polymercomposition was produced in the form of pellets similarly to Example 2,except for the following points.

Approximately similarly to Example 2, a raw material monomer mixedliquid 2 was prepared by mixing 93.0835 parts by mass of methylmethacrylate, 6.375 parts by mass of methyl acrylate and 0.076 part bymass of ethylene glycol dimethacrylate together, and adding thereto0.322 part by mass of n-octyl mercaptan as a chain transfer agent, 0.121part by mass of stearic monoglyceride and 0.013 part by mass of methylstearate as mold release agents, 0.0005 part by mass of di-tert-dodecyldisulfide as a thermal stabilizing agent, and 0.009 part by mass ofdimethyl 2-(p-methoxybenzylidene)malonate as an ultraviolet absorbingagent.

Approximately similarly to Example 2, a polymerization initiator mixedliquid 3 was prepared by mixing 99.752 parts by mass of methylmethacrylate, and 0.248 part by mass of t-amyl peroxy-2-ethylhexanoateas a polymerization initiator.

A polymerization initiator mixed liquid 4′ was prepared by mixing 90.280parts by mass of methyl methacrylate and 9.6 parts by mass of methylacrylate, and 0.120 part by mass of 1,1-di(t-butylperoxy)cyclohexane asa polymerization initiator which is different from the polymerizationinitiator in the polymerization initiator mixed liquid 4 in Example 2.

In this Comparative Example, a temperature in the first reactor 10 was140° C., and a temperature of the jacket 13 surrounding the outersurface of the first reactor 10 was set at 140° C., so that thecontinuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer (similarly to Example 2, a ratio offlow rates of the raw material monomer mixed liquid 2 and thepolymerization initiator mixed liquid 3 which were supplied to the firstreactor 10 was 16.7:1 and an average residence time in the first reactor10 was 46 minutes). A temperature of the jacket 16 of the connectionline 15 was set at 140° C. A temperature in the connection line 15adjacent to the supply port 21 a of the second reactor 20, in the otherwords, a temperature of the intermediate composition in the supply port21 a of the second reactor 20 was 140° C. Considering a temperature ofthe intermediate composition in the effluent port 11 b of the firstreactor 10 as the same temperature in the first reactor 10, i.e. 140°C., is allowable. In addition, a temperature in the second reactor 20was 175° C., and a temperature of the jacket 23 surrounding the outersurface of the second reactor 20 was set at 175° C., so that thecontinuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer (a ratio of flow rates of theintermediate composition and the polymerization initiator mixed liquid4′ which were supplied to the second reactor 20 was 18.3:1 and anaverage residence time in the second reactor 20 was 19 minutes). Theconditions in this Comparative Example are shown in Table 3.

Thus, the polymer composition was produced in the form of pellets (resincomposition). In this Comparative Example, similarly to Example 2, apolymerization rate (wt %) was determined from the supply weights perhour of the raw material monomer mixed liquid 2, the polymerizationinitiator mixed liquid 3, and the polymerization initiator mixed liquid4′, and the production (discharge) weight per hour of the pellets.Further, similarly to Example 2, the resin composition produced in thisComparative Example was molded to produce molded articles, and MFR (meltmass flow rate) and moldability were evaluated. Results of them areshown in Table 4.

Comparative Example 4

In this Comparative Example, generally, the polymer composition wasproduced without cooling in the connection line between the firstreactor and the second reactor and with adding a polymerizationinhibitor to the second reactor to inhibit the progress of thepolymerization reaction. More specifically, the polymer composition wasproduced in the form of pellets similarly to Example 2, except for thefollowing points.

Approximately similarly to Example 2, a raw material monomer mixedliquid 2 was prepared by mixing 95.0865 parts by mass of methylmethacrylate, 4.396 parts by mass of methyl acrylate and 0.076 part bymass of ethylene glycol dimethacrylate together, and adding thereto0.298 part by mass of n-octyl mercaptan as a chain transfer agent, 0.121part by mass of stearic monoglyceride and 0.013 part by mass of methylstearate as mold release agents, 0.0005 part by mass of di-tert-dodecyldisulfide as a thermal stabilizing agent, and 0.009 part by mass ofdimethyl 2-(p-methoxybenzylidene)malonate as an ultraviolet absorbingagent.

A polymerization initiator mixed liquid 3′ was prepared by mixing 99.767parts by mass of methyl methacrylate, and 0.233 part by mass of1,1-di(t-butylperoxy)cyclohexane as a polymerization initiator which isdifferent from the polymerization initiator in the polymerizationinitiator mixed liquid 3 in Example 2.

Differently from Example 2, the polymerization initiator mixed liquid 4was not used. Instead, a polymerization inhibitor mixed liquid 2 whichcomprises 2,4-dimethyl-6-t-butylphenol as a polymerization inhibitor inmethyl methacrylate at a concentration of 50 ppm by mass was prepared.

In this Comparative Example, a temperature in the first reactor 10 was175° C., and a temperature of the jacket 13 surrounding the outersurface of the first reactor 10 was set at 175° C., so that thecontinuous polymerization was conducted under an adiabatic conditionwith substantially no heat transfer (similarly to Example 2, a ratio offlow rates of the raw material monomer mixed liquid 2 and thepolymerization initiator mixed liquid 3′ which were supplied to thefirst reactor 10 was 16.7:1 and an average residence time in the firstreactor 10 was 46 minutes). A temperature of the jacket 16 of theconnection line 15 was set at 175° C. A temperature in the connectionline 15 adjacent to the supply port 21 a of the second reactor 20, inthe other words, a temperature of the intermediate composition in thesupply port 21 a of the second reactor 20 was 175° C. Considering atemperature of the intermediate composition in the effluent port 11 b ofthe first reactor 10 as the same temperature in the first reactor 10,i.e. 175° C., is allowable. In this Comparative Example, thepolymerization inhibitor mixed liquid 2 in place of the polymerizationinitiator mixed liquid 4 was stored in the polymerization initiator tank17. The polymerization inhibitor mixed liquid 2 was continuouslysupplied from the polymerization initiator tank 17 to the second reactor20 through the another supply port 21 c. The supply of the intermediatecomposition and the polymerization inhibitor mixed liquid 2 to thesecond reactor 20 was conducted so that a ratio of flow rates of themwas 18.3:1. In addition, a temperature in the second reactor 20 was 175°C., and a temperature of the jacket 23 surrounding the outer surface ofthe second reactor 20 was set at 175° C., so that the continuouspolymerization was conducted under an adiabatic condition withsubstantially no heat transfer (similarly to Example 2, an averageresidence time in the second reactor 20 was 19 minutes). The conditionsin this Comparative Example are shown in Table 3.

Thus, the polymer composition was produced in the form f pellets (resincomposition). In this Comparative Example, similarly to Example 2, apolymerization rate (wt %) was determined from the supply weights perhour of the raw material monomer mixed liquid 2, the polymerizationinitiator mixed liquid 3′, and the polymerization inhibitor mixed liquid2, and the production (discharge) weight per hour of the pellets.Further, similarly to Example 2, the resin composition produced in thisComparative Example was molded to produce molded articles, and MFR (meltmass flow rate) and moldability were evaluated. Results of them areshown in Table 4.

TABLE 3 Comparative Comparative Example 2 Example 3 Example 4 FirstPolymerization 140 140 175 reactor temperature (° C.) Half-life of 14 147 Polymerization initiator τ (sec) Average residence 46 × 60 46 × 60 46× 60 time θ (sec) τ/θ (—) 0.0051 0.0051 0.0025 Second Polymerization 140175 175 reactor temperature (° C.) Half-life of 14 7 — Polymerizationinitiator τ (sec) Average residence 19 × 60 19 × 60 19 × 60 time θ (sec)τ/θ (—) 0.0123 0.0061 — Temperature in the connection 105 140 175 line(° C.)

TABLE 4 Comparative Comparative Example 2 Example 3 Example 4Polymerization ratio (wt %) 55.1 57.5 55.9 MFR (g/10 min) 11 11 11Moldability 300° C. 0 0 0 (silver streaks 305° C. 0 0 30 occurrenceratio) (%) 310° C. 0 30 100

As understood from Table 4, Example 2 produced the polymer compositionhaving the better moldability (lower silver streaks occurrence ratio inthe molded article) than that of Comparative Examples 3 and 4 even whenmolded at a higher temperature (molding temperature higher than 300° C.,e.g. at 305° C. or more, further, e.g. at 310° C. or more), while thepolymerization rate was retained at an equal level and the MFR (whichmay give an indication for determining the molding conditions) wasretained at an equal level to those of Comparative Examples 3 and 4.

Industrial Applicability

The present invention can be used for producing a polymer compositionwhich is suitable for obtaining a resin composition comprising amethacrylic ester polymer(s).

The invention claimed is:
 1. A continuous polymerization apparatus whichcomprises, at least, a first reactor and a second reactor which are of acomplete mixing type, wherein each of the reactors is provided with asupply port, an effluent port, and a temperature detector for detectinga temperature in the reactor, the supply port of the first reactor isconnected to supply sources of a raw material monomer and apolymerization initiator, the effluent port of the first reactor isconnected through a connection line provided with cooler and a mixer tothe supply port of the second reactor.
 2. The continuous polymerizationapparatus according to claim 1, wherein the effluent port of each of thereactors is placed at the top of the reactor.
 3. The continuouspolymerization apparatus according to claim 1, wherein the supply portof the second reactor or another supply port provided to the secondreactor is connected to a supply source of an additional polymerizationinitiator.
 4. The continuous polymerization apparatus according to claim1, wherein the first reactor and the second reactor conduct a continuousbulk polymerization.
 5. A process for producing a methacrylic esterpolymer composition by using the continuous polymerization apparatusaccording to claim 1 which comprises: continuously supplying amethacrylic ester monomer as a raw material monomer and a polymerizationinitiator from the supply sources of the methacrylic ester monomer andthe polymerization initiator to the first reactor though the supply portof the first reactor to be subjected to continuous polymerization in thefirst reactor, and continuously taking a resultant intermediatecomposition from the effluent port of the first reactor, continuouslycooling the intermediate composition by the cooler of the connectionline during transport of the intermediate composition from the effluentport of the first reactor to the supply port of the second reactorthrough the connection line, and continuously supplying the cooledintermediate composition to the second reactor through the supply portof the second reactor to be further subjected to continuouspolymerization in the second reactor, and continuously taking aresultant polymer composition from the effluent port of the secondreactor.
 6. The process for producing a polymer composition according toclaim 5, wherein a temperature of the intermediate composition in thesupply port of the second reactor is 5-80° C. lower than a temperatureof the intermediate composition in the effluent port of the firstreactor.
 7. The process for producing a polymer composition according toclaim 5, wherein a temperature in the first reactor detected by thetemperature detector of the first reactor and a temperature in thesecond reactor detected by the temperature detector of the secondreactor are within the range of 120-150° C.